Abstract: A PC-based,interactive 3D-visualized off line-programming and simulation system was put forward.By use of 3D-graphical functions of Open GL,which is widely supported by current common PCs and popular operation system such as Windows,the 3D-geometrical model as well as the kinematical model of a robot and its workpiece was constructed in this system.Then the automatic path-planning and programming for robot,as well as the 3D-graphical dynamic simulation for robot movement was studied.With the function of interactive "virtual teach-in" procedure,the path-planning and programming for single-pass robot welding was implemented.For multi-pass welding,the welding path of each weld bead was automatically planned and programmed with "macro" technique.The robot motion path of the program could be verified for its reliability and security by means of 3D-graphical dynamical simulation.At last the program could be automatically converted to the particular language format of a robot when it is transferred to the robot system.Therefore the practicability of the off-line programming for robot was improved greatly.