Abstract: The 34CrNi3Mo steel roll produced by a company cracked during using. The causes for fracture failure of the roll were analyzed by macroscopic analysis, chemical composition analysis, mechanical property test, fracture analysis and metallographic examination. The results show that the failure mode of the roll was fatigue fracture. Under the complex alternating stress, the stress concentration was serious at the diameter variation position with large size change. The inhomogeneous central microstructure promoted the propagation of fatigue cracks and eventually led to fracture failure of the roll.