In order to achieve undersea target movement elements rapidly and precisely for active directional sonobuoy, the location arithmetic was improved and a method of target motion analysis based on Kalman filter was given. According to the characteristic of range-bearing location, the weighted average location arithmetic and its location error were given. The computation complexity of online least squares iteration was efficaciously decreased by this arithmetic. Then, a target motion analysis method based on Kalman filter was given. The target position, velocity and course were estimated by this filter. Finally, the considerable precision was confirmed by the results of Monte Carlo simulation.