The model of direction finding error and ranging error were established based on the principle and method of two-dimensional passive location. The analysis of error model show that, phase difference change rate error was the main influence factor of location error. In addition, not only the influence of relative position of target and observation station on azimuth error, but also the influence of direction finding error and phase difference rate error on distance measurement were analyzed. Finally, the relative ranging error of the ranging data was realized by using extended Kalman filter (EKF), which effectively improves the passive positioning accuracy of the moving observation station to the fixed target.