The joint section of a cut-off wall is a very important location and its quality is crucial to ensure the anti-seepage effect of the cut-off wall and determines the success or failure of the cut-off wall. The shortcoming of the traditional joint type is analyzed. From joint grouting principle of the dam body, a new reliable joint grouting of joint type is studied. Construction technics and technology key points are introduced. The feasibility, effect and benefit of the new joint are analyzed. This technology helps simplify the traditional joint construction technology, improve the efficiency of constructi on and shorten the construction period. Significant economic benefits are obtained.