The fire resistance ability of load-bearing column of building structure under fire is an important aspect affecting the safety of the structure. Although a large number of research results have been achieved in this respect, the researches on the numerical analysis of the bearing capacity and deformation process at high temperature are still not sufficient. The numerical simulation of the bearing capacity and deformation process at high temperature is hard to carry out and complex to operate, and not practical as well. Therefore, simplified analysis method is adopted to analyze the deformation and internal force of the controlling section of the load-bearing column subjected to fire. Besides, taking the concrete filled circular steel tubular column as example, the basic analysis theory of the fire resistance and the deformation performance of columns subjected to constant load is presented. The numerical calculation program which is developed on the basis of this theory can well simulate the process of deformation and the fire resistance of the columns subjected to fire. The simulation results are in good agreement with the experimental results.