Traditional safety surface generation algorithms have such problems as uncontrollable operation scalelong running timeand complex surfaceswhich can not meet the requirements of rapidity and reliability of airborne systems.In response to the above problemsthe safety surface generation algorithm is optimized by compressing the Digital Elevation Map(DEM)improving the terrain slope constraintand analyzing the longitudinal curvature constraint.Thentrajectory 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 algorithmsand the trajectory planned on the surface meets the requirements of helicopters in low-altitude penetration scenarios.