Beijing TIME Technologies Co.,Ltd. makes use of rectangular coordinate robot to carry submerged arc welding system for welding large structural workpieces,which has effectively improved the welding efficiency, reduced the work intensity and improved the welding quality. We solved the difficulties of integrating submerged arc welding system with Robot,and achieved good application results. The rectangular coordinate robot consists of a mechanical body,a robot controller and a welding system. The mechanical body consists of three linear axes and one rotating axle. The robot controller uses X86 industrial computer as hardware platform,and uses IEC61131-3 standard industrial control programming language to write control software to realize motion control algorithm and HMI.