Abstract: A continuous rotary north-finder is studied. Its formula of north-seeking and calculation are presented when under the state of no-attitude. In order to improve the north-finder's precision and performance, its sources of disturbance are analyzed. The signals of gyroscope and accelerator are sampled, FFT filter are adopted to the signals of gyroscope according to its characteristics and the processed results are compared with the original north-seeking result. Multi-cycle averaging method is adopted to deal with north-seeking result of each circle.The experimental results show that its north-seeking accuracy can achieve 0.008 3° within 340 s when it is leveled accurately.