Abstract: The crankshaft of the diesel engine broke and failed after the loader has been running for 1700 hours. The reasons of the crankshaft fracture failure were explored by means of the chemical composition analysis, hardness testing, metallographic structure analysis, fracture macroscopic and microscopic analysis, and other analytical methods. The results show that the failure mode of the crankshaft is high-cycle fatigue failure. The crack source is about 6 mm deep inside the journal of the 6th connecting rod of the crankshaft. The shrinkage defects which are not completely closed, and the large non-metallic inclusions (Ti,Nb,V)(N,C) which are clustered and distributed in bands inside the journal, are the main reasons for the crankshaft fracture failure. During the operation of the engine, the shrinkage hole defects acted as crack sources in the segregation zone of the (Ti,Nb,V)(N,C) non-metallic inclusions under the action of the service stress. The cracks grew and expanded to the internal cracks in the journal, and continued fatigue expansion to the final fatigue fracture failure.