Abstract: At present,China's Beidou geostationary satellites positioning system can only achieve two-dimensional active location,which greatly limits its application. A passive location method was put forward by using pseudolites to aid Beidou Geostationary Satellites Positioning System. The positioning theory of this system was discussed and the system time synchronization problem was analyzed. The effects of number and layout of pseudolites on the system accuracy were researched by mathematical simulation. The results show that the proposed method is feasible,which can enhance the usability,reliability,stability and the location precision of the system.