In order to solve the problems of M-pressure pump crankshaft fracture,full analysis of the M-pump caranshaft fracture was congducted. On this basis,stress analysis was carried out on the crankshaft by ANSYS. Through simulation analysis found that severe stress concentration sites coincide with the cleavage site,and conducted a simulation influence on the fracture of the crankshaft chamfer,and re-determine the size of the chamfer. To further verify the situation fracture,the fatigue strenth of frature section were checking calculation by analtical method. The results show,fatigue strength safety factor below allowable safety factor under the original conditions of the crankshaft 4mm chamfer,and fatigue strength safety factor to meet the design requirements in the case of 8mm chamfer. Improved design was performed according to the results of the simulation and calculation of the crankshaft,and applications significant effect,solved the problem of crankshaft fracture.