html:

<select ng-model="selected_cn_1" ng-options="value for (key,value) in countrys_1"></select>

js

$scope.countrys_1 = data.nationality;
$scope.selected_cn_1 = data.nationality[46];//通过ng-model和select绑定

ng-options usage

    <p class="am-form-group">
        <label class="am-u-sm-3 am-u-md-3 am-u-lg-2 am-form-label am-text-right">导演国籍:</label>
        <p class="am-u-sm-9 am-u-md-9 am-u-lg-10">
            <select id="direct-country" class="am-radius max-width-250" ng-model="selected_cn_0" number name="film[nationality]">
                <option value="{{k}}" ng-repeat="(k, v) in countrys_0">{{v}}</option>
            </select>
            <span class="am-form-caret"></span>
        </p>
    </p>

convert-to-number

    //http://stackoverflow.com/a/35407627/2586541
    app.directive('number', function () {
        return {
            require: 'ngModel',
            link: function (scope, element, attrs, ngModel) {
                //value
                ngModel.$parsers.push(function (val) {
                    //return '' + val;
                    return parseInt(val, 10);
                });
                //show
                ngModel.$formatters.push(function (val) {
                    //return parseInt(val, 10);
                    return '' + parseInt(val || 0, 10);
                });
            }
        };
    });