Abstract: This project proposes a multi terminal switching testing method based on wireless communication, provide new detection techniques for on-site testing. On the basis of handheld relay protection, the testing instrument is upgraded and modified by adding wireless communication interfaces to achieve wireless synchronous communication between two handheld testers. By setting the host and slave modes, the host sends synchronization signals to the slave at regular intervals to achieve synchronous output between the host and slave without the need for external clock synchronization. The problem of difficulty in simultaneously adding quantities to different interval devices in the same substation is solved through internal synchronization signals.