To solve the problems existing in those traditional path planning methods, the algorithm improves grid modeling method for global robotics path planning. Deep researches on scene modeling description, neighbor search and path search strategy are made. First, the linear octree method is applied to scene modeling. Second, hierarchical coding system based on linear octree is presented. Third, heuristic function is reconstructed by introducing path planning factor. In short, by hierarchical decomposition of scene based on octree, neighbor search based on linear octree codes, and improved A* algorithm, this algorithm can complete path planning and automated navigation in 3D virtual scene. The experiment results indicate that the algorithm is good in storage and time efficiency.