Abstract: Network performance is a hot issue in wireless sensor networks. How should the nodes be distributed to achieve good network performance? Many researchers have devised novel energy-efficient solutions to some of the conventional wireless networking problems, such as medium access control, routing, self-organization, bandwidth allocation and so on. In this study, some main performance indexes of wireless sensor networks are studied from a topology viewpoint. We study how to distribute sensor nodes and how many sensor nodes should be used in order to obtain a good network performance. Furthermore we adopt adaptive sleeping Medium Access Control (MAC) protocol SMAC for better energy efficiency. In this study, we build a general simulation platform using NS2 and design three typical topology structures innovatively and then research the network performance of wireless sensor networks in the three kinds of typical topology structure based on the platform. Simulation results verify the rules we have obtained in this study.