In order to study the influence of different factors on the current expansion speed of the thyristor during the turn-on process of the pulse condition, the equivalent circuit model of the pulse forming network based on the structural characteristics and working principle of the thyristor was established, and the simulation was carried out. Numerical simulation results show that if the forward blocking voltage increases from 3 000 V to 5 000 V, the spreading speed will increase by 24.6%. If the base width increases from 500 μm to 900 μm, the spreading speed will decrease by 31.7%. If the carrier lifetime increases from 1 μs to 10 μs, the spreading speed will increase by 56.9%. While the temperature increases from 300 K to 330 K, the spreading speed only increases by 0.3%. It can be seen that the temperature has little effect on the propagation speed. The research results are helpful to select appropriate parameters to ensure the expansion speed required for opening, and have application value for improving the design of thyristor devices and improving the performance of thyristors.