The path planned by the D* Lite algorithm is not smooth, and the preplanned path is very close to the known obstaclse. Besides, the replanned path is very close to unknown dynamic obstacles, so that the collision can happen very easily. To deal with the problem, the thoughts of the Lazy Theta* algorithm and distance transform are combined with the D* lite algorithm. Firstly, the map is processed by the distance transform algorithm to get the heuristic distance value, which makes the nodes that are far away from the obstacles preferred to be selected. Then, a line of sight algorithm is used while expanding nodes. The concepts of local parents and remote parents are added so that the path is more than eight neighbours. Finally, when unknown obstacles are discovered, the local distance transform algorithm is used to speed up the replan process and makes the replanned path safer. The experimental results show that the paths planned in different environments are all smooth and safe.