Abstract: Based on the acceptance criterion discussion for the 1E motor full voltage start- up characteristics used in nuclear power stations, this paper firstly simulated the switching transient response for the motor start-up LR circuit. The SIMULINK tool-FFT was used to process the current data and confirm the switching transient low-frequency modulation effect in the motor start-up process from the frequency domain. Then, the motor equivalent decomposition and superposition model was proposed. Though the equivalent decomposition, the relationship between full voltage start- up current and block running current was clear. Then based on much measured data, using Boltzmann model computer fitting, the conclusion was proved right. According to this paper, the acceptance criterion was unified at home and abroad basically.