The invention relates to an automatic welding and processing integrated machine for pipe installation and connection joint flanges, which includes a supporting base plate, a fixing device, a grinding device, a welding device, a rotating device and a post-welding processing device. The fixing device is installed in the middle of the supporting base plate Above, the grinding device is located above the fixing device, the grinding device is installed on the supporting base plate, the rotating device is located outside the fixing device, the rotating device is connected with the supporting base plate, the welding device and the post-welding processing device are installed on the rotating device, the welding device Located on the front side of the post-weld treatment unit. The present invention can solve the existing problems that the flange cannot be fixed multiple times when the flange and the steel pipe are welded, the flange is not firmly fixed, the flange needs to be manually polished before welding, and the flange is not polished before welding. Good, the welding action cannot be performed automatically, the post-weld treatment of the flange and the steel pipe is required manually, and the manual post-weld treatment is not thorough, etc.