Abstract: A structure of task-level OLP system is presented for arc welding robot, which consists of a modeler, a task programmer, a task planner and a robot motion simulator. We put forward a kind of classification for the features of welded structures, and on the foundation of AutoCAD14, using the technique of ObjectARX, develop the feature modeler for welded structures whose style is identical to the one of AutoCAD14. The synergetic expert system based on the combination of cases and rules is introduced to develop the task planner. Moreover, on the basis of 3DS MAX software, the essential robot motion simulator is developed with the language of MaxScript. The experiment shows that for some weld parts, efficient task-level OLP can be accomplished with our system.