Traditional north-finding gyroscope system based on transit method needs a whole gyroscope swing period which can not meet the modern measuring need for its long working time.The principle of 3/4 period transit method is proposed based on the whole transit method

then the basic principle and deduced formula of 3/4 transit method are presented.The contrastive experiments are accomplished based on JT15 gyroscope using the traditional transit method and the novel transit method.The experiments results show that 3/4 period transit method can effectively shorten the time of north-finding in the case of maintaining the measuring accuracy of the whole transit method.All of these prove the feasibility of north-finding gyroscope system based on 3/4 period and a new way to improve the north-finding efficiency time is put forward.