Abstract: In order to study the mechanical properties of self-compacting lightweight aggregate concrete under combined compression-shear loading, hydraulic servo machine and material compression-shear testing machine were used to study the uniaxial compression, uniaxial splitting tension and compression-shear composite loading of self-compacting lightweight aggregate concrete. The failure modes and force-deformation curves of aggregate concrete were compared with those of ordinary concrete and lightweight aggregate concrete under combined compression-shear loading. The results show that the failure modes of self-compacting lightweight aggregate concrete under combined compression-shear loading are different from those of ordinary concrete and lightweight aggregate concrete. Similarly, with the increase of axial compression ratio, the frictional trace of shear failure section is gradually obvious, and the concrete slag is also increased. At the same time, the shear failure strength, residual load and shear failure displacement of self-compacting lightweight aggregate concrete are gradually increased, and the shear failure strength affected by axial compression ratio is higher than that of ordinary concrete and concrete. While its residual load by axial compression ratio increases more than ordinary concrete, slightly lower than lightweight aggregate concrete. Based on the principal stress space and the compression-shear test data of ordinary concrete and lightweight aggregate concrete, the unified failure criterion equation of concrete under combined compression-shear loading was proposed, and the failure criterion of self-compacting lightweight aggregate concrete was proposed based on octahedron stress space. The proposed failure criterions have good applicability.