Abstract: Existing researches on discharge characteristics of compound intrinsically-safe circuits may be lack of mathematical analysis, or consider influence factors incompletely. For the above problems, discharge principle of compound intrinsically-safe circuit was analyzed, and mathematical models of discharge current, power and energy of the compound intrinsically-safe circuit under non oscillating state were derived. The influence of power supply voltage, inductance, capacitance, resistance and other parameters on discharge characteristics of composite intrinsically-safe circuit was simulated by Matlab software. The results show that with the increase of power supply voltage, the stable values of discharge current and power increase, and the discharge energy increases at the same time. With the increase of inductance, the blocking effect on current increases, and the discharge power and energy decrease gradually. In the initial stage, the discharge current, power and energy do not change with capacitance, and then gradually increase with the capacitance increase. The smaller the resistance R is, the greater the influence on the discharge current, power and energy is. Discharge current, power and energy decrease with the charging resistance R1 increases.