As one of the critical technologies in Internet of Things, the technology of wireless sensor network has gained increasing attention from both the research community and the actual users. As most of the nodes are generally battery powered devices, the energy is limited. As a result, one critical aspect to face is how to reduce the energy consumption of nodes, so that the network lifetime can be extended to reasonable times. In this paper the technology of wireless sensor network from three aspects: lower power, longer time and reliable transmission is depicted.