Abstract: A mathematical expression for the optical limiting threshold is derived according to the nonlinear absorption model. Based on the theoretical expression, the influence of optical physics parameters on the optical limiting effect, such as nonlinear absorption parameter, linear transmissivity and effective excitedstate absorption crosssection， were investigated with the experimental data obtained at the wavelength of 532 nm and in the pulse width of 40 ps by means of coordination polymer［Cd(L4)(SO4)(H2O)2］n. The research on the nonlinear optical properties and the optical limiting characteristics of the laser protection material provides the theoretical and experimental bases for preparing the much better optical limiting material.