The invention discloses a control method, device and system of an inverter. According to the embodiment of the invention, on one hand, the rotation speed of a motor rotor is calculated by utilizing an electric current model and/ or a voltage model, thus the estimated rotation speed is obtained, and on the other hand, the rotation speed of the motor rotor is measured by utilizing a speed sensor, thus the measured rotation speed is obtained; when the speed sensor is confirmed to be normal, and the rotation speed of the current motor rotor is at the high speed state or approaches to zero speed state, the actual rotation speed of the motor rotor is confirmed according to the measured rotation speed, while the speed sensor is abnormal, or although the speed sensor is normal, the current motor rotor is not only at the high speed state, but also approaches to the zero speed state, the estimated rotation speed is utilized as the actual rotation speed of the motor rotor; and then the output ofthe inverter is controlled according to the actual rotation speed of the motor rotor. In the scheme, appropriate speed sources are selected according to different occasions and different operation states of the motor, and the rotation speed of the motor rotor is obtained accurately.