Due to short of pre-charge, a high power semiconductor switch reversely switching dynistor (RSD) suffers from switching-on locally. Based on the direct pre-charge circuit, a new two-step switching method is introduced. The conditions for the normal turn-on of RSD are analyzed and the model of RSD in a cell structure is built. The model simulation shows that the RSD has better performances: shorter width pre-charge current, and reduced recombination of plasma during the pre-charge. Two-step switching experiment indicates that a proper preliminary turn-on current is important for uniformly switching-on the RSD, and the reverse pre-charge current works mainly for switching preliminary forward current. Simulation and experimental results both show that two-step switching increases RSD uniform turn-on characteristic compared with the direct pre-charge circuit, because the stored charges inside are increased obviously by two-step switching.