diff --git a/src/cascader/demo/index.vue b/src/cascader/demo/index.vue
index 09b6222fa..00b8157ba 100644
--- a/src/cascader/demo/index.vue
+++ b/src/cascader/demo/index.vue
@@ -99,12 +99,13 @@
   </demo-block>
 </template>
 
-<script>
-import zhCNOptions from './area-zh-CN';
-import enUSOptions from './area-en-US';
+<script lang="ts">
 import { computed, reactive, toRefs } from 'vue';
+import { CascaderOption } from '..';
 import { useTranslate } from '@demo/use-translate';
 import { deepClone } from '../../utils/deep-clone';
+import zhCNOptions from './area-zh-CN';
+import enUSOptions from './area-en-US';
 
 const i18n = {
   'zh-CN': {
@@ -147,10 +148,17 @@ const i18n = {
   },
 };
 
+type StateItem = {
+  show: boolean;
+  value: string | number | null;
+  result: string;
+  options?: CascaderOption[];
+};
+
 export default {
   setup() {
     const t = useTranslate(i18n);
-    const state = reactive({
+    const state = reactive<Record<string, StateItem>>({
       base: {
         show: false,
         value: '',
@@ -182,7 +190,7 @@ export default {
 
     const customFieldOptions = computed(() => {
       const options = deepClone(t('options'));
-      const adjustFieldName = (item) => {
+      const adjustFieldName = (item: CascaderOption) => {
         if ('text' in item) {
           item.name = item.text;
           delete item.text;
@@ -201,15 +209,21 @@ export default {
       return options;
     });
 
-    const loadDynamicOptions = ({ value }) => {
+    const loadDynamicOptions = ({ value }: CascaderOption) => {
       if (value === '330000') {
         setTimeout(() => {
-          state.async.options[0].children = t('asyncOptions2');
+          state.async.options![0].children = t('asyncOptions2');
         }, 500);
       }
     };
 
-    const onFinish = (type, { value, selectedOptions }) => {
+    const onFinish = (
+      type: string,
+      {
+        value,
+        selectedOptions,
+      }: { value: number | string; selectedOptions: CascaderOption[] }
+    ) => {
       const result = selectedOptions
         .map((option) => option.text || option.name)
         .join('/');
diff --git a/src/cascader/index.js b/src/cascader/index.tsx
similarity index 82%
rename from src/cascader/index.js
rename to src/cascader/index.tsx
index 1fb2d0435..ba1fe73fd 100644
--- a/src/cascader/index.js
+++ b/src/cascader/index.tsx
@@ -1,4 +1,4 @@
-import { nextTick, reactive, watch } from 'vue';
+import { nextTick, PropType, reactive, watch } from 'vue';
 import { createNamespace } from '../utils';
 
 // Components
@@ -8,15 +8,34 @@ import Icon from '../icon';
 
 const [createComponent, bem, t] = createNamespace('cascader');
 
+export type CascaderOption = {
+  text?: string;
+  value?: string | number;
+  children?: CascaderOption[];
+  // for custom filed names
+  [key: string]: any;
+};
+
+type CascaderTab = {
+  options: CascaderOption[];
+  selectedOption: CascaderOption | null;
+};
+
+type CascaderFieldNames = {
+  text: string;
+  value: string;
+  children: string;
+};
+
 export default createComponent({
   props: {
     title: String,
     modelValue: [Number, String],
-    fieldNames: Object,
+    fieldNames: Object as PropType<CascaderFieldNames>,
     placeholder: String,
     activeColor: String,
     options: {
-      type: Array,
+      type: Array as PropType<CascaderOption[]>,
       default: () => [],
     },
     closeable: {
@@ -29,7 +48,7 @@ export default createComponent({
 
   setup(props, { slots, emit }) {
     const state = reactive({
-      tabs: [],
+      tabs: [] as CascaderTab[],
       activeTab: 0,
     });
 
@@ -40,7 +59,10 @@ export default createComponent({
       ...props.fieldNames,
     };
 
-    const getSelectedOptionsByValue = (options, value) => {
+    const getSelectedOptionsByValue = (
+      options: CascaderOption[],
+      value: string | number
+    ): CascaderOption[] | undefined => {
       for (let i = 0; i < options.length; i++) {
         const option = options[i];
 
@@ -109,7 +131,7 @@ export default createComponent({
       ];
     };
 
-    const onSelect = (option, tabIndex) => {
+    const onSelect = (option: CascaderOption, tabIndex: number) => {
       state.tabs[tabIndex].selectedOption = option;
 
       if (state.tabs.length > tabIndex + 1) {
@@ -165,15 +187,19 @@ export default createComponent({
       </div>
     );
 
-    const renderOptions = (options, selectedOption, tabIndex) => {
-      const renderOption = (option) => {
+    const renderOptions = (
+      options: CascaderOption[],
+      selectedOption: CascaderOption | null,
+      tabIndex: number
+    ) => {
+      const renderOption = (option: CascaderOption) => {
         const isSelected =
           selectedOption && option[valueKey] === selectedOption[valueKey];
 
         return (
           <li
             class={bem('option', { selected: isSelected })}
-            style={{ color: isSelected ? props.activeColor : null }}
+            style={{ color: isSelected ? props.activeColor : undefined }}
             onClick={() => {
               onSelect(option, tabIndex);
             }}
@@ -189,8 +215,8 @@ export default createComponent({
       return <ul class={bem('options')}>{options.map(renderOption)}</ul>;
     };
 
-    const renderTab = (item, tabIndex) => {
-      const { options, selectedOption } = item;
+    const renderTab = (tab: CascaderTab, tabIndex: number) => {
+      const { options, selectedOption } = tab;
       const title = selectedOption
         ? selectedOption[textKey]
         : props.placeholder || t('select');