A sensorless control method and system for a motor are provided. The includes a back EMF observer that is configured to estimate a back EMF of the motor and an angle error calculator that is configured to calculate an electrical angle error considering iron loss of the motor based on the back EMF estimated by the back EMF observer. An angle error compensator is configured to compensate the electrical angle error calculated by the angle error calculator. An electrical angle for compensating the calculated electrical angle error is obtained through simulation or experiment for the motor. In addition, a PLL controller is configured to receive the compensated electrical angle to estimate an actual angle by reducing the electrical angle error due to the iron loss, and to operate the motor based on the estimated actual angle.