Abstract: Granular lubrication is a new lubrication method which can be used in severe environments, while the shear dilatancy characteristics of granular flow lubrication are the key obstacles that remains unsolved in fully setting up the granular lubrication theory. A granular flow lubrication analytical model based on the discrete element method is proposed. Using this model, the variation rule, speed adaptation mechanism, and stress adaptation mechanism of shear dilatancy in the lubrication startup phase are studied, and the mechanical mechanism of shear dilatancy was obtained by analyzing the influence of shear velocity and pressure load on the shear dilatancy. The results show that in the lubrication startup phase, the shear dilatancy rate of granular flow lubrication system exhibits a quadratic polynomial law with time steps. The shear dilatancy amplitude of granular flow lubrication system all gradually decreases with increased shear velocity and pressure load, respectively. The shear dilatancy characteristics of granular flow lubrication is closely related to the fluctuation of force chains between granular lubrication medium. When the fluctuation amplitude of force chains increases, the variation amplitude of shear dilatancy for granular flow lubrication system also increases, and vice versa. Distribution of contact forces between granular lubrication medium is found to obey a power law, and the strength of force chains increases with the increased absolute value of shear dilatancy rate.