The C102B reciprocating piston compressor is an important equipment widely used in methanol production. Because of the complexity of exact dynamics analysis, the traditional and common way to find the reason of fracture is only based on metallographic structure analysis of crosshead material. In this paper, after metallographic structure analysis of crosshead material of the C102B compressor, the maximum loads on it are also calculated and two dangerous crosshead positions with maximum load are determined. Finally, stress analysis of the crosshead in two dangerous positions is implemented by FEM technology. Based on the above study, the reasons of crosshead fracture of the C102B compressor are found. The results has an inportant significance for judging the resaon of crosshead failure.