The invention provides a Buck circuit parameter determination method and a Buck circuit parameter determination device. The Buck circuit parameter determination method comprises the steps of: firstly,determining a duty ratio, and acquiring an inductor inductance initial value and a capacitor capacitance initial value based on a switching frequency initial value; and then judging whether the inductor inductance initial value and the capacitor capacitance initial value meet an intrinsic safety requirement, so as to obtain a final inductor inductance value, a final capacitor capacitance value and a final switching frequency. The Buck circuit parameter determination method and the Buck circuit parameter determination device can guarantee that a Buck circuit satisfies ripple performance requirements, and can enable the Buck circuit to meet the intrinsic safety performance requirement; the inductor inductance initial value and the capacitor capacitance initial need to be subjected to judgment of intrinsic safety requirement, and the precision of the final inductor inductance value, the final capacitor capacitance value and the final switching frequency is significantly improved; and aninductor is separated from a capacitor by utilizing extremum solution, complicated iterative solution process is not required, the process is simple and the implementation is easy.