Abstarct: In this project the Doppler and bearing tracking as one kind of passive tracking discusses. The importance of passive tracking is the observer invisibility, and being observable is the importance of Doppler and bearing tracking. So there is no need any maneuver for the observer. But the problem of this kind of target tracking is nonlinear measurements equation, from this problem it is difficult to find appropriate approach for solving this problem. So in this research first we investigated all the approaches for solve this problem then we chose the best approach and then according to the criteria that we consider, the best approach is the optimal approach, and finally we introduce Kalman filter is the optimal approach for solving this problem. Then we discussed kalman filter problems and present new approaches for reducing Kalman filter problems.