The most important purpose of grid networks is resource subscription in a dynamic and heterogeneous environment. They are accessible through using various methods. Subscription has mainly computational, scientific and other implications. In order to reach grid purposes and to use available resources in grid environment, subtasks are distributed among resources and are scheduled by considering the quality of service. It has been tried to distribute subtasks between resources in a way that maximum QOS can be obtained. In this study, a method has been presented. In this method, three parameters; namely, sent and transferred time between RMS and resource, process time of subtask by the resource, and the load of available tasks in resources row, have been taken into account. In this way, multi-criteria decision is made by using TOPSIS method and this priority of the resources are determined to assign them to subtasks. Finally, time response, as an efficient parameter, has been improved and optimized by optimal assignment of the resources to subtasks.