从能级角度出发，结合入射激光脉宽对粒子吸收方面的影响，用速率方程模拟了各能级粒子数的瞬时变化关系，给出了激光脉宽与能级寿命可比拟时反饱和吸收的动态解，表明粒子在能级上的分布情况。用C60和HITCI(1,1',3,3,3',3'-hexa methyl lindo tricarbocyanine Iodide)的实验参数理论模拟了激发态吸收截面大于基态吸收截面时透射率随光强的变化关系，用以说明大的上能级吸收截面可以抑制光强过大时引起的饱和吸收，增强材料的非线性光限幅特性。

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.