In order to realize the goal of improving the efficiency of autonomous trajectory planning during long-range penetration of aircraft, in view of the characteristics of radar threat distribution under the background of this mission, the subdivision grid theory is used to organize the grid environment, and the A* algorithm is improved from the underlying characterization mode.The code of the split grid is used to characterize the organizational structure to obtain the orientation information, thereby imposing a penalty factor in a targeted manner, and the cost calculation method of the actual moving path is improved based on the directivity.Then, according to the characteristics of radar threat distribution, the sub-nodes are found by using the variable step size in sections based on the variation of comparative coding bit.The simulation results show that the node computation of the improved algorithm is greatly reduced, and under the condition that the total cost value of the trajectory sought is approximate, the improved algorithm can always obtain a feasible trajectory more quickly in the environment with dense threat distribution, which is well suited to the background of aircraft penetration.