Abstract: The plastic tee pipe set at the bottom of the excavated canal section of the South-to-North Water Diversion Project is the key component of the connection between the check valve and the permeable concealed pipe at the canal foundation. In the restoration project of South-to-North Water Diversion Project’s canal,in order to form dry land restoration conditions,this paper proposes implementing gasbag plugging at this position to effectively block the connection of concealed pipes in the canal to form a relatively closed area so as to facilitate the maintenance of channel lining boards. The tee pipe of the main canal in the middle route of South-to-North Water Diversion Project is used as the prototype to carry out the equal scale indoor plugging test. Combined with the finite element software ABAQUS for numerical simulation,the stress distribution and evolution law of the plastic of plastic tee pipe under the local internal pressure formed by plugging gasbag are studied,and the strength evaluation is carried out. According to the analysis,the stress concentration of the tee pipe under the internal pressure of gasbag mainly appears on the shoulder and abdomen of the inner of the tee pipe.When the water level in the canal is 6m,that is,the upper limit of the pressure generated by the gasbag is 0.06 MPa,the tee pipe will not yield and produce local failure. So,it is considered that the tee pipe is safe and stable. The research results can provide a basis for the safety evaluation of tee pipe when gasbag is used for plugging in the channel repair project of South-to-North Water Transfer Project.