Abstract: Switchgear is a piece of power supply equipment directly oriented to users, thus the evaluation of the working state of switchgear is of great significance to the accurate assessment of the reliability of power supply. This paper designed a method to evaluate the change trend of the working state of switchgear based on TEV differential comparison according to the requirements for live detection of switchgear and in combination with the principle of horizontal and vertical comparison, proposed effective criterion for state trend from such aspects as amplitude deviation and pulse number deviation, and developed a joint electroacoustic detection and treatment scheme for partial discharge of switchgear to accurately predict the severity and change trend of partial discharge and evaluate the working state of switchgear in a given period. At last, the practical case of the detection of 10KV switch station was applied to prove that the above-mentioned criteria and method for state trend are effective and feasible.