Substation is the hub of electric energy conversion and distribution, in which the primary equipment lightning arrester can reduce the overvoltage of electrical equipment, so as to protect the power system. The high voltage arrester consists of single-phase and multi-section small units in series. The traditional measurement of single-section arrester units requires the removal of a high voltage lead, which takes a long time and has a large security risk. Based on this, the 220kV zinc oxide double-section arrester is taken as an example to design a safety test system for detecting the working condition of the high-voltage arrester. The test data of the corresponding arrester unit is measured through the conversion connection of the control relay, and a weak signal acquisition algorithm is proposed under complex electromagnetic conditions to accurately extract the current of each frequency. At the same time, optical fiber communication is used to read and display the leakage current value in real time. The test results show that the system can accurately measure the leakage current value of high voltage arrester, which is in line with the high voltage industry standard and has high application value.