Abstract: The purpose of the study on soil structure is to find a quantitative index which can comprehensively reflect the characteristics of particle arrangement and cementation of soil.By means of the laboratory triaxial consolidation drainage shear tests on the mechanical properties of sand under different particle arrangements, the influences of different particle arrangement on the mechanical properties of structural sand are studied, the stress-strain characteristics were summarized and analyzed, and the effects of the particle arrangement on the strength of sand are studied.The results show that the internal friction angle of the samples with high relative compaction is higher than that with low relative compaction.When the relative compaction is the same, the internal friction angle of the mixed samples is obviously higher than that of the other samples;the strength is the largest when the particles of the samples are arranged from large to small(from bottom to top), on the contrary, the strength is the minimum.This study is of good guiding significance for engineering practice, especially for foundation filling projects such as highways and railways.