Pipeline transportation plays an important role in the resources deployment and economic development of our country. Its dimensional repair technique is an important guarantee to ensure the safety and reduce the loss. Tapping machine draws a lot of attention as the key equipment. According to project practice, key problems of the largest-diameter pipe tapping machine's design and manufacture in our country was discussed. Firstly, the development Status, opportunities and challenges was analyzed. Then, the requirements and theory of tapping machine design were analyzed; the design of features, accessories and control components was finished. The problems of tapping with pressure, pressure balance, body seal and remote control was solved. Finally, the problems in the manufacturing process of tapping machine like welding, deep hole and keyway in long axis were researched and the solutions were put forward. The successful use of the machine shows its usefulness and reliability.