Abstract：An improved potential field theory was used to plan three dimensional paths for airplane. The potential field theory was optimized with the aim of effectively evading not only radar threat and fire threat, but also terrain threat, which made three dimensional flight path planning have certain practicality. Simulated terrain elevation data was overlapped with radar threat and fire threat in accordance with their weights respectively to form integrated threat electric field, and the weights of terrain threat and radar threat, fire threat were determined according to the needs of given penetration task. Through locating the search area between start point and end point, it is ensured that the final flight path can be restrained on end point; at last, the above paths were smoothed by gradient smooth algorithm and curvature smoothing limitation algorithm on acceleration and curvature, so that the performance of paths can be in line with the requirements of maneuverability and flying. The simulation results show that the optimal potential field theory can further consider terrain threat and other threat (radar threat and/or fire threat) near end point, which improves the method's practicability, and deduces the planning time.