Abstract: Objective The aim is to develop an off-line programming system for welding robots based on SolidWorks and improve software versatility and off-line programming efficiency. Methods Firstly, the system selects weld seams through manual interaction, analyzes characteristics of welds and extracts the information. Secondly, according to the shape of weld seams, straight line, circular interpolation algorithm or cubic polynomial interpolation method are used to fit and generate welding trajectory. Thirdly, based on welding process and combined with interpolation point information, welding gun’s initial attitude is determined by calculating the attitude matrix at the interpolation point with perpendicular method or normal vector orthogonal method. According to the user’s adjustment of welding gun’s attitude, quaternion-based spherical linear interpolation can be used to interpolate welding gun’s attitude in the neighborhood to optimize welding gun’s attitude. Finally, the system establishes robot coordinate system by an improved D-H method and obtains inverse solution of the robot by Pieper criterion to complete the design of welding simulation module. Results The system ensures smooth of welding gun’s movement and improves welding quality. Conclusion The proposed off-line programming system effectively enhances versatility and off-line programming efficiency of software, which provides a feasible solution for welding robot automation and intelligent manufacturing.