In view of the shortcoming of traditional systematic calibration method depending on precision of turn-table, based on the basic e-quation of navigation velocity error and inertial error parameter of instrument, the relationship between directional components of navigation velocity error and inertia error parameter of instrument was deeply analyzed, the principle of selecting calibration position was proposed; The relationship between navigation velocity error and mechanical SINS gyro bias parameter was derived, error parameters affecting acceleration of mechanical SINS were deeply analyzed through the output model of mechanical SINS, the systematic calibration methods of mechanical SINS and optical SINS were united. The simulation results show that this method has good identification precision, reduces the requirement for turn-table precision and improves usability of calibration equipment.