TDMAbased protocol called RTDMA saves energy consumption of effectively by introducing reservation mechanism. Only if significant changes of environmental data have been detected did nodes apply to the cluster head for reservation，and then upload data; Otherwise nodes will in dormant state as much as possible, so as to save energy. Referring to Rockwell’s model WIN, energy consumptions of TDMA, ETDMA and RTDMA are simulated; results show that the increasing number of nodes or events in the network does not brings a dramatic changes of energy consumption. The performance of RTDMA in energy saving, compared with TDMA and ETDMA, is improved significantly.