Abstract: In view of the crack in tee fitting in the formation from B10 copper alloy plate, the crack analysis is carried out by chemical composition analysis, mechanical property analysis, metallographic structure analysis, energy spectrum analysis and fracture scanning. The results show that the crack has obvious bifurcations and presents the characteristics of intergranular propagation. There are three characteristic areas of red, dark red and gray at the grain boundaries near the crack. The grain boundary at the end of the crack is obviously widened and there are a few precipitated phases. The formation of Cu-rich phase or precipitated phase at the grain boundary leads to the weakening of the grain boundary, which is the main reason for the cracking of tee fitting in the forming process from B10 copper alloy plate. There are defects in local parts of the plate, which provides a prerequisite for the generation and propagation of crack. The process control and inspection should be enhanced in the ingot smelting and plate preparation.