Abstract: With energy level and the influence of incident laser pulse width on particle absorption taken into consideration, the instantaneous relationship of the particles on each energy level was simulated with the theoretical rate equation. The dynamic solution of reverse saturable absorption was given when the laser pulse width was comparable to the lifetime of energy level, which indicated the particle distribution at the energy levels. The variation of the transmittance with the light intensity was theoretically simulated with the experiment parameters of C60 and HITCI when the cross section of the excited-state absorption was larger than that of the ground-state absorption. It indicates that the larger upper energy level absorption cross section can restrain the saturation absorption caused by intense light. The nonlinear optical limiting of the optical materials was improved.