Uplift of pipeline due to buckling deformation and the resultant soil resistance are key concerns in its design. This paper investigates the particle-size effect on uplift resistance of a pipe buried in sand and the ground deformation mechanism using the distinct element method (DEM). Two granular grounds, one for coarse-sand ground and the other for fine-sand ground, were examined in this simulation. The results show that both cases exhibit similar deformation mechanism of four featured stages: mobilization of peak uplift resistance, infilling of soils beneath pipe, formation of shear bands, and flow of soils around pipe. The uplift resistances in both cases gradually increase to a peak and then drop to a constant value with the upward displacement of the pipe. However, higher peak resistance and shear bands with gentler slope are observed in the coarse case.