A robot simulation system has been developed as a debugging tool for industrial robot task programming. This system simulates the RHINO XR-2 robot motion graphically on HIPLOT DMP-29 Multi-Pen plotter, which makes the assessment of robot motion possible. The joint variable vectors are calculated from the position and orientation of the endeffector with respect to the reference coordinate system by inverse kinematics. The functions required for this robot simulation system are to keep the robot geometric model, and to generate motion data for the geometric robot model in Cartesian coordinates. All of these robot motions are drawn from starting (home) position to desired final position by means of orthographic projection method. This system has been implemented in "C" language on VAX-11/780 mini-computer system running under UNIX (4.2BSD).