Research is carried out on output signal of simplified rotation-modulated gyro north seeker based on sequential robust estimation.Fundamental principle of the north seeker is introduced

on the basis of classical sequential adjustment method

computation procedures and formula of sequential robust estimation is deduced combining the theory of robust M estimation.Divide output signal of north-seeker to two parts

above method is simulated and applied.Simulation result shows that the mean error and standard error of north seeking result gained by the deduced algorithm is better than other algorithms.