Abstract: The recycled waste tire rubber particles mixed with sand have the advantages of low density, strong distortion-resistant capacity and high damping. The mixtures are becoming a kind of new geotechnical material, which realizes the sustainable development of civil engineering. In this study, the influence law and mechanism of the rubber content XC, particle size ratio of rubber and sand d_{50, r}/d_{50, s}, relative density D_r and confining pressure σ'_m on the shear resistance of mixtures are evaluated by a series of consolidated undrained tests. The results show that the failure mode shows a transformation from partial softening-dilatancy to complete hardening-contraction with the increase of XC. In general, the increase of XC will lead to a significant decrease of (σ₁-σ₃)_f and the internal friction angle, and an improvement of the effective internal friction angle to a certain extent. The closer the rubber particle size is to the sand, the more obvious the influence is. In addition, the increase of D_r can significantly improve the shear strength characteristics of the mixtures. Based on the micro-soil skeleton structure, the experimental phenomenon and its laws are preliminarily explained.