The P92 hot extrusion tee with 85000 hours of service crack is taken as the research object. Its size is mapped by 3D optical scanning technology. Based on the mapping size, the finite element stress analysis is carried out, and the stress intensity assessment is carried out according to ASME Ⅷ - 2. The results show that the three-dimensional optical mapping size of P92 hot extrusion tee is in good agreement with the actual size, the maximum stress is located in the corner center of the shoulder inner wall, which coincides with the opening position of 85000 hours in service. The weak structural strength of the shoulder is the strength factor that causes the cracking of P92 hot extrusion tee. In the manufacturing quality control and metal supervision and inspection of the hot extrusion tee, it is important to check the shoulder .