Based on the discharge inductance model, the transient characteristics of capacitive rectifier system of pulsed homopolar inductor alternator are analyzed, and all four operating modes of this rectifier system are clarified. The critical voltage between modes and the formulas for calculating commutation delay angle and overlap angle are derived, and a transient model is established. The accuracy of the proposed theoretical calculation is verified by valve-to-valve circuit simulation and experimental results. The function of each mode in the circuit to the charging process is expounded, and the equivalent form of circuit is analyzed, and reveals the design principle of the charge voltage and the amplitude of motor electromotive force (EMF). The results of the study show that: the circuit can be seen as a form of charging a capacitor by serially connecting a DC source with an equivalent commutation reactance and an equivalent transient commutation inductance; mode 1 and mode 2 play a major role in the whole charging process; the reasonable charge voltage should be between 1.3 times and 1.5 times of the amplitude of generator′s phase EMF.