Abstract: Described here in the essay is the development of the Φ1 400 mm×1 200 mm X80 prefabricated sleeve Tee for service at-45℃,involving the development background and the R & D process as well as the welding equipment for circumferential weld.Tested are the properties of the circumferential weld of the said product.Thanks to taking the measure of prefabricating and welding sleeves at both ends of Tee main pipe,the welding quality of the butt weld is improved,the stress concentration in the circumferential weld position is reduced,and the bearing capacity of the weld is enhanced.Meanwhile it is also convenient for the construction site to realize the equal wall thickness connection of the butt circumferential weld.