High speed railway catenary is an important infrastructure of high-speed railway, and its safety is related to the passenger life and property safety. This paper proposed a tension sensor that can be used for on-line monitoring of high-speed railway catenary. The sensor uses solar cells to supply power and sends the measured tension data to the terminal for monitoring by wireless module. The results show that, The measuring range of our tension sensor is 30kN, and the measurement accuracy can reach 2.1% F.S.. Also, our tension sensor has passed the lateral slip test of 3kN, which is a necessary experiment for the installation of high-speed rail lines.