As the inertial measurement unit (IMU) error calibration of the laser gyro strapdown inertial navigation system has high requirements on the precision of the turntable, the base north alignment and leveling, and considering the factors such as the jitter of the laser gyro, the temperature rises under long time working, and the complexity of the algorithm during the system operation, a systemlevel calibration method using the speed as the measurement value and the least square fitting method was proposed in this paper. Through three axis turntable to process multiposition measurement: stationaryrotationstationary, 24 error parameters, such as installation error, sensor zero bias and the scale factor between threeaxis laser gyro and threeaxis accelerometer have been rapidly identified. The whole calibration process takes about 2 hours, with the multiposition alignment heading, roll, pitch accuracy of higher than 0.012°. The experiment shows that the proposed algorithm is simple and the operation process is convenient, and the IMU precision of the laser gyro strapdown inertial navigation system can be improved effectively.