Abstract: To investigate the effects of power supply voltage on dynamic performance of servo amplifier with current feedback, the servo amplifier's two models: linear model and nonlinear saturated model were constructed and the effect of the power supply voltage on the set up time of servo amplifier controlled current was studied by given different step inputs. As the power supply voltage on servo amplifier was increased, the set up time for controlled current was reduced. But the set up time reduction slowed observably, as the power supply voltage was increased to about 3 times as large as the servo amplifier output voltage corresponding to rated current. If the efficiency of servo amplifier is considered, it is practicable that the power supply voltage is about 3 times as large as the servo amplifier output voltage corresponding to rated current.