To solve the problems that heading error and velocity error of inertial navigation system (INS) increase and the heading angle of the great circle route changes rapidly in polar regions, a calculating method of polar navigation parameters for INS was proposed. First, the polar heading error restraint mechanism was studied and a ellipsoid grid heading reference model was built. Then, the calculating of grid heading and grid velocity was implemented using the calculating navigation parameter information of INS. Finally, the polar navigation performance evaluation of the method was completed. Theoretical analysis and simulation results show that the calculating  method is simple, the calculating navigation parameters  are conducive to polar sailing monitoring and plotting, and the precision of grid heading and velocity is superior to that of the geographic heading and velocity, which illustrates that the method could meet the requirement of polar navigation and improve the polar navigation performance of the inertial navigation system.