Abstract: In view of problem of low positioning accuracy of wireless sensor network positioning system，a design scheme of underground precise positioning service system based on CSS was presented．The hardware structure, CSS precise positioning algorithm and specific work process of the system were introduced．The system uses CSS precise positioning technology based on TDOA, and can accurately locate the position of terminal，and send data via WCDMA 3G communication module to cloud computing services platform，so that users can use any Web browser platform to obtain the terminal location information. The simulation experiment results indicate that the system can improve positioning accuracy greatly and reduces error compared with other underground positioning systems.