Abstract: Wireless sensor networks integrate sensor technology, MEMS technology, wireless communication technology, embedded computing technology and distributed information management technology. Because of wide application prospect, it interested the world. This paper introduced the composition of node, the system frame of wireless sensor networks and the research of hot spots. And it expatiates the application in agriculture, and brings forward the way of application in greenhouse, irrigation, precision farming and so on. All of these are expanding the thinking of application in agriculture and putting the wireless sensor networks into use in the field of agriculture earlier.