Traditional safety surface generation algorithms have such problems as uncontrollable operation scalelong running timeand complex surfaceswhich can not meet the requirements of rapidity and reliability of airborne systems.In response to the above problemsthe safety surface generation algorithm is optimized by compressing the Digital Elevation Map(DEM)improving the terrain slope constraintand analyzing the longitudinal curvature constraint.Thentrajectory planning on the surface is conducted.Simulation results show that the improved safety surface generation algorithm reduces unnecessary calculations with efficiency increased by about 3~6 times in comparison with traditional algorithmsand the trajectory planned on the surface meets the requirements of helicopters in low-altitude penetration scenarios.