The actual north seeking precision has declined significantly due to heading effect of north seeker. On the basis of introducing the principle of FOG north-seeker, the method of FOG four position north seeker under the large angle of inclination was given. Aiming at the calculated azimuth, the quadrant distinguishing method was proposed. Meanwhile, the heading effect of fourposition north seeking method in the range of 0 to 360 degrees was analyzed theoretically with a presentation of error compensation method. The conclusion was obtained that the largest error of north seeker heading effect exists with the sensitive axis of gyroscope pointing to north and south directions. Finally, the correctness and validity of the north-seeking method, the theoretical analysis and the compensation method were proved through simulation.