Abstract: To more scientifically and accurately determine the wall thickness and other design parameters of big-diameter X80 T-joint for long-distance pipelines, verification test method research is carried out by using a series of physical burst tests for X80 T-joints. Wall thickness reduction coefficient K of main T-branch tube subject to plastic forming is used to build design calculation formula of big-diameter T-joint wall thickness to determine wall thickness and other design parameters of big-diameter X80 T-joint and form technical requirements of X80 T-joint for the Third West-to-East Gas Pipeline Project. As shown from research results, the recommended X80 big-diameter T-joint wall thickness is much less than the wall thickness determined by the area reinforcement method. The recommended method not only reduces costs of raw materials and production difficulty, but also further improves the product quality, which provides a basis to the design and manufacture of the big-diameter T-joint for pipeline projects in the future.