Aiming at the problems such as hysteresis and large calculation amount during path planning of moving targets we put forward a path planning method suitable for moving target in dynamic environments.First of all the Kalman filter algorithm was used to estimate the next position of the target.Then the D* algorithm was used for the path planning of the UAV by taking its current position as a starting point and the targets predicted position as a destination.In order to reduce the prediction error and ensure efficient route planning the dynamic observation periods were used.Since the Kalman filtering algorithm predicts the next state of UAV according to a recursive formula it doesnt need a lot of historical data(one at most).The prediction algorithm can not only reduce the calculation cost but also has strong real-time performance.The simulation results show that the algorithm can effectively shorten the distance and reduce the time needed for getting to the target position.