In the storage tank shell straight seam welding, due to the common welding robot's structure is complicated, expensive and high maintenance cost, therefor the special automatic welding device is designed. The device was based on and applied the integration of the robot into the traditional welding equipment design concept, which used the SIEMENS S7-200 type programmable logical controller (PLC) control system and Panasonic MINAS-A5 server driver. The welding device system could precisely control the welding position, and implement automation welding production goal. It can solve the actual production problem of the small and medium-sized enterprises, at the same time, in the practical application of manufacturing the robotized machine can provide the reference value.