Abstract: In order to study the specific damage forms of reinforced concrete (RC) frame columns in the plastic hinge zone, this paper proposes five collapse failure modes of RC frame columns under horizontal and vertical loads based on Mohr--Coulomb criterion with tension-cutoff. Then the critical conditions and the distribution of three typical collapse failure modes of RC columns among the five modes are derived and determined by structural parameters like the height width ratio and the axial compression ratio as the main influence factors, and it is shown that the mode b is the most common collapse failure mode of the RC frame columns. Some experimental results in literature are used to verify the above theoretical conclusions, which will provide a theoretical basis for the lateral displacement calculation of the RC frame columns under the earthquake action and for the anti-collapse design.