Abstract: In order to investigate the effect of sandy soil gradation on its shear properties, direct shear tests were conducted for four types of different artificial gradation of sandy soil samples made of the standard sand. The numerical shear tests were conducted for DEM samples that have the same gradation with the four artificial sand samples. The test results show that the influence of particle gradation on the internal friction angle is significant; generally, the internal friction angle increases with the non-uniformity coefficient, and decreases with the curvature coefficient. The DEM tests show that the initial sandy soil gradation has significant effect on the porosity ratio, particle coordination number and the particle slide fraction; in addition, the failure of sandy soil is a progressive process that depends on the particle gradation; the dilatancy coefficient decreases at the beginning and increased later with increase of the parameters of d10, d30and d60.