Three kinds of critical state models, such as Bean's model, Kim's model and Power model, are selected to analyze numerically the initial magnetic curve and hysteresis loop of Bi2223 high-Tc superconductor, as an example, with a simple method. Programs are made to calculate the magnetization as a function of applied magnetic field and temperature. The results are discussed compare the three kinds of critical state models. The hysteresis losses of superconductors at different temperatures and under different amplitudes of applied magnetic field are studied according to functions derived using these models.