Abstract: This paper presents the study of establishing the relevant discriminants of the internal intrinsic safety performance evaluation of Buck converter. Firstly, the arc discharge of a simple inductor circuit was taken as the research object. Based on the thermal ignition theory, the temperature field model of the continuous heat point heat source was adopted, and the spark discharge time threshold expression used to determine whether the spark can successfully ignite the gas mixture was obtained, which was based on the condition that whether the time interval that the initial combustion volume decreases from the highest value to the combustion temperature of the gas mixture is longer than the time of the chemical reaction. Secondly, based on the explosive test data, the expression of the inductive open arc discharge energy of Buck converter calculated by the equivalent resistance method and the discharge current linear model was corrected. Furthermore, the energy discriminant and discharge time discriminant of the intrinsic safety performance evaluation of the Buck converter were established. The verification results show the rationality of the critical value of the discharge time and the correctness of the established discriminants.