Abstract: This study attempts to investigate the strength behavior of plain high-strength high-performance concrete (HSHPC) subjected to biaxial compression load with seven stress ratios  =  2﹕ 3 = 0.00: 1, 0.20: 1, 0.30: 1, 0.40: 1, 0.50: 1, 0.75: 1, 1.00: 1. In the above cases, temperature loads are also applied, they are 20℃, 200℃, 300℃, 400℃, 500℃ and 600℃ respectively. Biaxial tests were carried out on 100mm×100mm×100mm cubic concrete specimens, then, the biaxial compression strengths were measured, and failure modes of specimens were inspected. Moreover, the influence of high temperature and stress ratio on the biaxial strength was also analyzed. Experimental results show that the uniaxial compression strength of plain HSHPC doesn’t decrease with the increasing of temperature at 200℃ and 300℃, and the ratio of the biaxial strength over uniaxial strength depends on stress ratio and brittleness-stiffness of HSHPC. Finally, the formula of the Kupfer-Gerstle failure criterion for plain HSHPC considering temperature and stress ratio is proposed.