Abstract: In order to realize the pipeline (ϕ 813 mm) between the Sichuan-to-East Gas Pipeline and the 2nd West-to-East Gas Pipeline connected without shutdown, it is necessary to design the ϕ 813-ϕ 914-ϕ 1 016 interconnection 4-way fitting which is applicable to hot tapping. The fitting strength design meets the opening reinforcement principle of pressure vessel and the overall structure resembles the shape of "上". The 4-way fitting is equipped with ring segment and completion plug in order to achieve the fitting self-sealing after the hot tapping and facilitate the disassembly of the auxiliary valve and hot tapping equipments. To satisfy the requirements of pipeline pigging and pigging test during pipeline's daily operation, the baffle bar is designed to ensure the permeability after the hot tapping and the geometric integrity of inner pipeline wall and reduce the influence of hot tapping on the pipeline to the uttermost. And it is shown from its field application that the ϕ 813- ϕ 914-ϕ 1 016 interconnection 4-way fitting can meet the requirement of pipeline connection without shutdown, reaching the expected design target.