Abstract: A transverse fracture accident occurred during the operation of the roller shaft of a cement roller press. The fracture causes were analyzed by means of design and operation verification, macroscopic observation, chemical composition analysis, metallographic examination, scanning electron microscope analysis and mechanical property test. The results show that the impact absorption energy of the roller shaft matrix was low, resampling at the same position of the matrix and testing again after high temperature tempering treatment, the impact absorption energy of the sample increased significantly, which determined that insufficient tempering during the quenching and tempering process was the root cause of the brittle fracture of the roller shaft.