Abstract: In passive tracking system, the method using bearings-only can't determine the position of target quickly with high precision. What is more, the EKF is traditional algorithm for passive tracking, but it produces large errors and easily leads to divergence. This paper introduces a new method using phase difference rate and SR-UKF algorithm. It can amend aforementioned flaws, lead to filter stability in use, and significantly improve the performance of tracking. The method is validated by the results of the simulation experiment.