Abstract: By means of optical microscope and scanning electron microscope, the cracked mould for connecting rod forging was analyzed including fracture analysis, nonmetallic inclusion detection, hardness testing, macroscopic detection of cross section, metallographic examination of crack source and the position of 1/4, 1/2 (core) of cross section from crack source. The results showed that the main cause of early brittle fracture of mould was material segregation and stress concentration caused by serious tool marks. Meanwhile, the suggestions were put forward.