The switched reluctance generator (SRG) has intrinsic spatial and magnetic nonlinearities, making it challenging to design an output voltage controller with accurate tracking performance. This article proposes a linearization technique to improve the voltage control of SRG. A linearization block, which describes the nonlinear relation between SRG's phase current reference and averaged output current under various speed conditions, is added in the control loop. The linearization block's analytical expression is derived according to the electromechanical conversion principle of SRG. The experimental results show that, thanks to the linearization, the settling time is divided by more than two during transients, compared with the classical methods that ignore the nonlinearities. The performance of the voltage tracking is also significantly improved: the mean absolute error for load or voltage change is improved by more than 60% and 30%, respectively.