Используйте этот код.
<input type="button" id="btnget" value="Show Popup" />
<div class="modal fade" id="mymodal">
<div class="modal-dialog">
<div class="modal-content">
<div class="modal-header">
<button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">×</span></button>
<h4 class="modal-title">Modal title</h4>
</div>
<div class="modal-body">
<select id="veggies" multiple="multiple">
<option value="cheese">Cheese</option>
<option value="tomatoes">Tomatoes</option>
<option value="mozarella">Mozzarella</option>
<option value="mushrooms">Mushrooms</option>
<option value="pepperoni">Pepperoni</option>
<option value="onions">Onions</option>
</select>
</div>
</div>
</div>
</div>
$(function() {
$('#veggies').multiselect({
includeSelectAllOption: true
});
$('#btnget').click(function() {
$('#mymodal').modal('show');
})
});
Код Css-
.multiselect-container>li>a>label {
padding: 4px 20px 3px 20px;
}