Aiming at the problem that the current three-axis gyroscope calibration relies on expensive turntable equipment or the calibration parameters are incomplete, a method based on a two-step correction method is proposed. Firstly, the six-position method is adopted to calibrate and compensate the 12-parameter model of the accelerometer, the scale factor of the triaxial gyroscope, and the static bias of the three-axis gyroscope. Then, the non-orthogonal error model of the triaxial gyroscope is formulated for the system-level calibration. The two-step correction method can quickly and accurately identify various errors without precision equipment, and obtain a good calibration effect. Simulation experiments show that the average non-orthogonal error obtained by this algorithm is close to 1% , the standard deviation is less than 0. 1% , the average scale factor error is less than 0. 14% , and the standard deviation is less than 0. 004% . The actual experiment shows that in the attitude update results of 65 s pure inertial navigation, the pitch angle error and the roll angle error of this calibration method can reach 0. 624° and 0. 67°.