Abstract: Recent advances in sensing techniques, embedded computing techniques, distributed information processing techniques and communication techniques have enabled the development of wireless sensor networks. As there is a bright future in their application, wireless sensor networks have become a new research area in the 21 century. There are large numbers of challenge problems in science and engineering in the wireless sensor network area. Since 2000, more and more researchers have been engaged in the research work on wireless sensor networks and a lot of research results have already been obtained. Suiveyed in this paper is the research work on wireless sensor networks, including the wireless sensor network communication techniques, infrastructure techniques, middleware techniques, data management techniques, sensor node and embedded software techniques. The existing problems in the current research work and the new research issues are also discussed. At the end of the paper, many significant references are listed for the researchers.