In order to explore an indirect line-of-sight stabilization technology of vehicular gunner's periscopic sight, advantages and disadvantages of traditional direct stabilization method were analyzed. On the basis of this, a method of indirect LOS stabilization based on inertial navigation equipment was proposed. From the output of inertial navigation equipment on land vehicle, the attitude information of vehicle could be achieved, and the disturbance information of gunner's periscopic sight was obtained by coordinate transformation from the attitude information. Then the disturbance information was sent to LOS control unit to keep the LOS be relatively stable to the inertial space. Experiments were taken to validate indirect LOS stabilization ability of vehicular gunner's periscopic sight. The experiments results show that the method is correct and practical, and has the same precision with the direct LOS stabilization method.