Abstract: In this paper, a study of the mechanical parameters in fretting fatigue was made. The mechanical parameters in fretting fatigue were divided into two kinds, which were stress state parameters (SSP) and fretting wear parameters (FWP). The equivalent stress σ_-1E was formulated for the effects of SSP on fretting fatigue. The friction work W was used to express the effects of FWP on fretting fatigue. On the basis of boundary element methods, the numerical analysis of specimens, which were bridge-line fretting-fatigue specimens and dovetail joint specimens, showed that the parameters σ_-1E and W were relatively large in the vicinity of fretting fatigue crack.Therefore, it is possible to take the equivalent stress σ_-1E and friction work W as the twO basic parameters of predicting the fretting fatigue failure.