Since the single observer passive tracking algorithm using bearing measurement only has some disadvantage such as slow location speed, low location accuracy. The single observer passive tracking problem with bearings and their changing rate measurements was studied, and the extended Kalman filter (EKF) in the modified polar coordinate (MPC) was adopted to track the target. The tracking results of using bearing measurements only and using bearings and their changing rate measurements were compared in the same simulation condition. The simulation results show that the location speed and location accuracy all can be improved through using bearings and their changing rate measurements to track the target in the modified polar coordinate.