Single observer passive localization and tracking is a useful technique in the fields of aviation, spaceflight and navigation. Some algorithms with higher precision and fast speed improves the performance of localization and tracking system significantly. EKF algorithm is the most classical method in numerous nonlinear dynamic systems, and successfully applying in many passive localization problems. However, it sometimes produces large errors and easily lead to divergence. Alternative algorithm of Kalman filter, such as UKF, is introduced to amend flaws of the EKF, and has better properties of robustness and accuracy. The computer simulations are carried out, and the results indicate that the UKF performs better than the EKF.