Aiming at the failure of the local horizontal geographic frame in high latitudes, the inertial navigation algorithm was reorganized in the grid frame, and the inertial navigation error equation in the grid frame was also analyzed. Based on the characteristics of RLG rotational inertial navigation system, the simulation experiments and practical experiments are designed to verify the effectiveness of the INS algorithm in the grid frame. The experiment results show that the grid frame can be used as the navigation frame to solve the computational problems caused by the convergence of meridian in high latitudes.