TDOA and SDS-TWR are commonly used ranging methods in UWB indoor positioning systems, aiming at the difficulty of clock synchronization in TDOA and the slow speed of SDS-TWR ranging in hardware, a new ranging method based on the fusion of TDOA and SDS-TWR is proposed. This method divides the known anchor nodes into communication master node and secondary node, and can directly measure the communication time from the master node to the target node and the time difference between the target node and the secondary node required for positioning, and the distance between all anchor nodes and the target node in the positioning area can be calculated accordingly. Through error analysis, it is found that the proposed method is accurate enough in indoor positioning, and the simulation results show that its positioning accuracy is within 25cm, which is smaller than the error of TDOA ranging and improves the slow speed of SDS-TWR ranging.