The invention relates to a rotor position error estimation method of a permanent-magnet synchronous motor without a position sensor. The rotor position error estimation method comprises the followingsteps of (1) constructing a sliding-mode observer of a permanent-magnet synchronous motor-based Gamma/Delta-axis coordinate system, and acquiring a rotor position error; (2) measuring the corresponding rotor position errors of the permanent-magnet synchronous motor under different rotational speeds with regard to different rotational speeds, and fabricating a one-dimensional table of the rotor position errors relevant to the rotational speeds; and (3) looking-up the table to obtain the rotor position error according to the rotational speed of the motor, and obtaining the rotor position by estimating and summing difference between the rotor position and the rotor position error, wherein the rotor position participates in operation of a permanent-magnet synchronous motor control system. By the rotor position error estimation method of the permanent-magnet synchronous motor without the position sensor, the rotor position estimation accuracy of a traditional algorithm of the permanent-magnet synchronous motor without the position sensor can be remarkably improved.