Abstract: Iron loss of silicon steel sheet for converter motor at the condition of different frequencies was studied. The effect of annealing temperature and time on the iron loss at the condition of different frequencies was discussed. The results show that frequency variation of the motor has obviously effect on the ratio eddy current loss to total iron loss of silicon steel sheet, and the effect of annealing time on the hysteresis loss of power frequency and high frequency is different rules. At the condition of high frequency (400 Hz), the eddy current loss ratio is significantly higher than that of the power frequency (50 Hz). Annealing at 980℃, the iron loss at the condition of power frequency is the lowest, while the increase of annealing temperature can lead to the increase of iron loss at high frequency. With the increase of annealing time, the hysteresis loss at the high frequency can be reduced, but the hysteresis loss can be increased. The above results can provide research foundation for the control of the iron loss of silicon steel for converter motor.