A surface acoustic wave based distribution transformer temperature on-line monitoring system comprises a surface acoustic wave sensor array, a receiving antenna, an energy obtaining module, a central processing module and a communications module. The surface acoustic wave based distribution transformer temperature on-line monitoring system can perform distributed real-time monitoring on the temperature of a distribution transformer, thereby effectively avoiding the occurrence of accidents of heat damage to the distribution transformer and improving the operational reliability of a distribution network. In addition, large-scale use of the system can facilitate dynamic capacity increasing of the distribution network, improve the transmission capacity of a unit distribution network line, decrease new lines and reduce infrastructure costs. Furthermore, the system has the advantages of being high in temperature measurement accuracy and low in cost and the like.