方法1:

<!-- ng-model 设置所选择的默认值  -->
<select class="form-control col-md-6" ng-model="model.qc_type"  ng-options="item.id as item.relationtype for item in relationTypeData">

</select>

方法2：

<select class="bs-select form-control" ng-model="filter.status" ng-options="item.id as item.cardType for item in cardTypeData">
   <option value="" selected hidden></option>
</select>