Abstract: Bei dou" double-star positioning system is a kind of regional positioning system. But because of the limitation of the number of satellites, double-star system cannot realize the real-time 3-D passive positioning. In this paper, a new idea of using pseudolites to augment the double-star system is put forward, and the algorithm and geometry of this augmented positioning sysem is studied. The simulation results indicate that the idea of double-star system augmentation with pseudolites is feasible and can fulfill the real-time passive positioning with the high precision independently, which offer a new way to develop the independent regional satellite positioning system at a relatively lower cost.