According to equipment distributional characteristics and structure of distribution power grid（DPG）， a DPG monitoring communication network topology based on wireless sensor network（WSN） is introduced. By analysis demand of DPG monitoring and control data， an enhanced QoS-MAC model based on IEEE 802.15.4 protocol is built for WSN requirement of power industry communication specification. The model is expressed by node buffers Markov chain model and wireless channel probability calculation model for providing QoS. In order to analyze WSN performance of DPG， CSMA/CA channel collision model， communication time-delay model and network data throughput model in MAC layer supported by QoS are calculated. The network analysis scenarios for distribution devices communication are also designed to analyze the network performances for QoS-MAC under different distribution data rates. The analysis and application results show that the method proposed can provide effective QoS for DPG monitoring and communication control.