In order to solve the MOS photoelectric coupling circuit of mini solid state relay with switch triggered by mistake when the upper loop no action, the principle of mini solid state relay is analyzed and researched. Meanwhile, it summarizes the working principle and static features of MOSFET field-effect tube. Based on the characteristics of the circuit, the loop capacitor charge and discharge dynamic process is deduced when switch opening and closing. The reasons for false triggering are identified, and then this driving circuit with higher safety performance improvement measures is put forward. The test results show the reliability of the measures. The experimental results prove the validity of the theoretical derivation transient process and measures of feasibility. These improvement measures provide a new circuit scheme for photoelectric MOS gate mini solid state relay. It also can effectively decrease DC project outage caused by interface circuit fault.