Motor torque control method and system and air conditioner

The invention provides a motor torque control method and system and an air conditioner. The method comprises the steps that the q-axis current and the rotating speed of the motor are determined according to a three-phase current value, and the speed change of the motor is obtained through calculation according to calculation parameters, the q-axis current and the rotating speed; determining a rotating speed threshold according to the q-axis current and a preset mapping relation; wherein the rotating speed threshold value comprises a first rotating speed threshold value and a second rotating speed threshold value; and according to the speed change, the rotating speed, a rotating speed threshold value and a preset speed change threshold value, the torque control state of the motor is determined, and the torque of the motor is controlled according to the torque control of the corresponding state, so that the output torque of the motor is equal to the load torque of the compressor. In the control mode, the two ro