With Multiple Spanning Tree Protocol (MSTP) defined in IEEE802.1s, the Common Spanning Tree (CST) and additional Spanning Trees could be configured to take on load balancing in switch networks. For achieving balance distribution in traffic flows, we proposed an optimizing strategy to determine the MSTP parameters configuration in single regions. The strategy optimizes load balancing and shows its efficiency through computational results of instances. We compared the MSTP solutions in various flow load instances, and the result shows that the optimizing strategy takes an efficient load balancing when traffic flows are mainly between switches belonging to the same region.