Abstract: Tests of reinforced concrete (RC) members subjected to compression (tension), bending and shear indicated that the strength depends on the loading condition. By introducing the shear-force term into the compression (tension)-bending interaction equation, the paper presents a strength formula considering the overall interactions of compression (tension), shear and bending. The formula reasonably reflects the real stress state of members and agrees well with the experiment data. Finally, strength envelope of the compression (tension)-bending interaction equation was drawn according to the formula. The strength envelope can be used to obtain the stress state of member easily and evaluate the condition of members under combined compression (tension), shear and bending. It can be used as a criterion to determine the member dissociation in the collapse analysis.