Please custom the datagrid view and override the 'setEmptyMsg' method.
var myview = $.extend({}, $.fn.datagrid.defaults.view, {
setEmptyMsg: function(target){
var state = $.data(target, 'datagrid');
$.fn.datagrid.defaults.view.setEmptyMsg.call(this, target);
state.dc.view.children('.datagrid-empty').css('top', '50%');
}
})
$(function(){
$('#dg').datagrid({
view: myview,
emptyMsg: 'no records'
})
})