angularjs uses ng-change to implement checkbox change trigger events, and uses ng-checked to implement selection but does not trigger the ng-change event. It can only be triggered when manually clicked, which roughly means that only when the checkbox in <td> is directly clicked To trigger add(), add() is invalid when clicking the checkbox in <th> to implement multi-selection in <td>checkbox
The code is as follows

<tr>
  <th><input type="checkbox" ng-model="isChecked"></th>
</tr>
<tr ng-repeat="item in data track by $index">
  <td><input type="checkbox" ng-checked="isChecked" ng-model="item.isChecked" ng-change="add(item.isChecked,item.uid)"></td>
</tr>

var uid_list = [];
    $scope.add = function (item_checked,uid) {
        var uid = parseInt(uid);
        if(item_checked){
            uid_list.push(uid);
        }
        if(!item_checked){
            var index = uid_list.indexOf(uid);
            uid_list.splice(index,1);
        }
        console.log(uid_list);
    };