The shortcomings of active positioning mode of Chinese Beidou navigation satellites system are introduced while a new technology is proposed on the basis of time difference carrier phase (TDCP) for RDSS/SINS tightly coupled integration. The TDCP measurements are used as the observation of Kalman filter to establish a tightly coupled integrated navigation system that works in passive mode. The principles and mathematic model of TDCP are described and a Kalman filter for integration is designed. Static and dynamic state tests were performed to validate the algorithm and evaluate the accuracy. The results show that the accumulation of velocity errors and position errors are attenuated remarkably.