Aiming at the parameters calibration of the fine tuning Stewart mechanism for the secondary mirror of the optoelectronic telescope, based on the previous calibration method, first of all, a method for calibrating model of Stewart mechanism is proposed based on the inverse kinematics model, which avoids the problem of the difficulty of solving the forward kinematics, the low efficiency of numerical solution and the error of the numerical solution. Secondly, the problem of solving the calibration model is analyzed, and the Jacobian matrix is solved and an improved Gauss-Newton iteration method and a specific experimental procedure are presented for the case that the model coefficient matrix is not reversible. Finally, the effect of measurement error caused by the least square principle is analyzed, the calibration simulation experiment on the designed Stewart mechanism is carried out by using the Matlab. The results show that the calibration accuracy is increased by 56 times when the measurement error is less than 0.1 μm, the average precision is only increase by 7.8 times when the measurement error is less than 1 μm. After the calibration of the prototype, the average position precision is increased by 30.77 times, and the attitude accuracy is increased by 20.73 times. The more accurate structure parameters of Stewart mechanism can be obtained by using the optimization proposed calibration method, which can effectively improve the accuracy of position and attitude.