For the strong electromagnetic pulse(EMP) simulation device using a coaxial Tesla transformer as a pulse driving source, synchronous injection into the Tesla primary winding is an effective way to enhance the output effect, which is of great significance to optimize the performance of the EMP simulation device. In this paper, focusing on the primary injection structure of a typical coaxial-type Tesla transformer, the current distribution and corresponding resistance and inductance parameters of the primary winding under different injection conditions are studied, and the advantages and parameter requirements of multiple injections are analysed. Based on the reverse-polarity capacitor-discharge trigger, the trigger simulation model is established to analyse the influence of loop isolation parameters on the triggering effect, and it is appropriate to use capacitive isolation, and the capacitance value should be much larger than the capacitance value of the switching structure. Multiple injections can significantly reduce the resistance value of the primary winding, improve the uniformity of current distribution, and reduce the inductance of the primary winding, in order to improve the output efficiency and reduce the weight of the magnetic core.