Abstract: Since the main drive asynchronous motors of the MPM are of the frequency converter AC drive type,the requirement for design of the motor's capacity is rather stringent. Elaborated in the article are the capacity calibration and the mechanical characteristics of the main drive variable frequency asynchronous motor of the 14" MPM located in Pangang Group Chengdu I & S Co.,Ltd. Addressing the required on-load torque for operation with rpm higher than the rated value,a new calculation method for capacity calibration of the said motor is proposed.