In this paper, the closure-welded joint is studied through experiment after canceling telescopic joint of penstock in the hydropower station at dam toe. The closure-welded joint includes butt joint and lap joint and each has its own characteristics. According to calculation and experiment, these two joints can meet the requirements of design. There are little axial contraction and low restraint stress in the lap joint. Using some technologies, the restraint stress in butt joint can be reduced and cracks can be prevented. The lap joint has more complex stress distribution and higher stress concentration factor than butt joint. It is advantageous for safe running of penstock to use butt joint.