Abstract: Most underground positioning systems can only provide regional positioning function and are unable to provide accurate real-time location information for personnels or equipments, a design scheme of underground precise positioning system based on CSS technology was proposed. The system uses SDS-TWR localization algorithm and positioning management protocol to get high positioning accuracy. Meanwhile, it does't need to do clock synchronization, which enhances realizability and stability of the system. The testing results show that the system realizes high-precision positioning for underground equipments and personnels, which positioning accuracy is less than 3 m and the farthest transmission distance is 350 m.