A model-based off-line programming system of the robot operations is developed for industrial use. Environment modelling system based on the solid modelling system GEOMAP-III, is developed as a tool for maintaining the information of the working environment of the robot, such as robot itself, parts to be assembled, obstacles, etc., and other necessary information for the robotic tasks. A high-level assembly description language which describes assembly process in terms of the operations on the parts to be assembled instead of motion of the robot itself, is designed. By utilizing the information of the environment model, the system generates information of the robot motion from this high-level description, simulating the changes in the environment. Feasibility checks of the generated robot motion, detection of collisions between the robot and obstacles, calculation of necessary grasping force, are performed in the process and the results are displayed to the operator for easy debugging of the program. Preparation for sensory interactive robot motion in the run-time system, is also considered. As examples, some assembly operations are programmed by the system with high-level language.