Abstract: In order to explore the mechanical properties of self-compacting lightweight aggregate concrete under biaxial loading, the three axis test machine was used to carry out biaxial compression-compression and biaxial tension-compression. The stress-strain curve and its failure form under different working conditions were obtained. The peak stress and peak strain of the stress-strain curve were extracted, and the ordinary concrete and the lightweight aggregate concrete in the related literature were obtained. The biaxial mechanical properties of self-compacting lightweight aggregate concrete was compared with research results of ordinary concrete and the lightweight aggregate concrete. The results show that the specimen mainly presents the shear failure mode when the lateral pressure is low, and the specimen is split when the lateral stress is high. Under the condition of biaxial tension-compression, the specimen is mainly splitting failure, which is independent of lateral stress. With the increase of lateral pressure stress, the main compressive stress of the self-compacting lightweight aggregate concrete is obviously higher than that without lateral stress, the maximum increasing of peak stress is 68.08%, and the main tensile stress gradually decreases with the increase of lateral pressure stress, and the maximum decrease is 62.35%. Using the Kupfer biaxial stress failure criterion, it is proved that the influence of the lateral stress on the self-compacting lightweight aggregate concrete is more conservative. At the same time, the failure criterion of the self-compacting lightweight aggregate concrete biaxial mechanical properties was proposed based on Kupfer. The failure criterion equation has good applicability.