Hysteresis behavior of magnetic force versus gap between a high-T c superconductor and a magnet, in static and dynamic cases, is studied numerically. Differing from the previous methods, based on macro electromagnetic constitutive relation of superconductors and Maxwell equations, a numerical method with the finite element method (FEM) is established. After numerical code is examined by comparing between numerical and experimental results of the relation of magnetic force-gap, the hysteresis curves of magnetic force-gap including major and minor loops in static case are simulated, and furthermore the dependences of major loop on main parameters including the critical current density and the thickness of superconductor, the residual magnetic field of magnet, and the diameter ratio of superconductor to magnet are studied numerically. In the case of free vibration, by investigating dynamic response of levitated body at different levitation/suspension positions in this magnetic levitation system, we obtain the corresponding results of the variation of magnetic force with gap. All the numerical results of the relation between magnetic force and gap show the strongly nonlinear and highly hysteretic behavior.