The 'loader' function contains all the request parameters sent to server. Please override it to get these parameters.
$('#dg').datagrid({
	loader: function(param, success, error){
		console.log(param)
		var opts = $(this).datagrid('options');
		if (!opts.url) return false;
		$.ajax({
			type: opts.method,
			url: opts.url,
			data: param,
			dataType: 'json',
			success: function(data){
				success(data);
			},
			error: function(){
				error.apply(this, arguments);
			}
		});
	}
})