The finite element method software ANSYS was used to analyze the mechanism of fatigue of rail surface short crack under the different operating statuses including friction free,pure rolling and complete sliding,and the effect of friction coefficient on the propagation rate of contact fatigue crack was analyzed.The results show that,the mixed mode of wheel/rail contact crack includes sliding mode and opening mode,and the most dangerous location of opening mode crack is at the edge of the contact area.With the increase of the crack angle,the stress intensity factor KI is increased,but the KII is decreased.The rate of crack propagation with 60° angle is the fastest.The crack propagation rate is increased significantly with the increase of the friction coefficient.It is safety to buff the rail surface by using the buffing period calculated based on the 60° crack.