In order to solve the problems of long demagnetization time,high required voltage and large equipment required of traditional AC demagnetization equipment, a low-voltage AC degaussing method based on sinusoidal pulse width modulation(SPWM) technology is proposed based on the analysis of the residual magnetization of the converter transformer and the traditional demagnetization principle. Using high stability SPWM digital power supply technology and high computing performance microcontroller, the AC voltage amplitude and frequency is output from SPWM by digitally controlling to achieve the purpose of obtaining a large AC demagnetization current under low voltage conditions and being able to accurately adjust the current amplitude, while the low voltage conditions can greatly reduce the size and weight of the equipment and shorten the demagnetization time. Using quasi-synchronous sampling technology without phase-locked loop and without strict synchronization requirements, high-precision measurement of the effective value of AC voltage and current in a wide frequency range is realized. A degaussing and verification device for the converter transformer is developed and a degaussing test is carried out for the converter transformer with residual magnetism. The results show that the demagnetizing inrush current after demagnetization is significantly reduced, reflecting the significant degaussing effect of the device. A degaussing effect verification method is proposed by connecting the low-voltage AC test voltage to the converter transformer and comparing the no-load current of the transformer before and after degaussing. The test results show that the verification method is effective and feasible.