Abstract: A motor drive system includes an electric motor, a drive circuit and a control unit. The drive circuit provides a driving current to the electric motor. A current command generator of the control unit generates a current command according to a torque command and a motor operating information. The driving current is converted into a d-axis current and/or a q-axis current by the control unit. Consequently, the driving current is close to the d-axis current command and/or the q-axis current command corresponding to the current command. If a value of the torque command is positive, the current command generator generates the corresponding current command according to a MTPA lookup table. If the value of the torque command is negative, the current command generator generates the corresponding current command according to a zero recycle lookup table.