Abstract: In wireless sensor networks (WSNs), the many-to-one communication mode, mutual interference of wireless links, dynamic changes of network topology and the memory-restrained characteristic of node, all make network more vulnerable to congestion. Since network congestion may deteriorate the transmitting performance and network lifetime, congestion control has become one of the most important technologies to decrease such impact and guarantee the network quality of service (QoS). Because the energy supply, computational power and wireless communication capabilities of sensor nodes are all limited and the network scale is always very large, higher requirements are imposed on the congestion control technology and researches on congestion avoidance and congestion release are more challengeable. This paper is a survey of congestion control technology for wireless sensor networks. In this paper, the main characteristics of wireless sensor networks, and causes and damages of network congestion are presented, and then three kinds of congestion detection strategies based on data buffer length, wireless channel sampling and data transmitting rate, and two kinds of congestion avoidance mechanisms based on data rate allocation and buffer announcement are introduced. The classical congestion release algorithms based on rate control, flow schedule and transport schedule are analyzed, and finally the development trend and future prospect of congestion control technology for wireless sensor networks are presented.