Abstract: High signal-to-noise ratio(SNR)is very important in the interaction between high energy ultra-short laser and materials.In order to increase the SNR of ultra-short laser,the saturation absorption property of Nd:glass laser at the neighborhood of 800nm was studied.The relationship between the nonlinear transmissivity and normalized energy density of the combined Nd:glass system was obtained after solving the rate equations.For an optional 800nm laser pulse,making use of the frequency differences between amplified spontaneous emission pulse,modulation pulse and the main laser pulse,combining different types of Nd:glass material of optimizing the comprehensive data of the density,thickness.etc,the absorption spectrum of the combined Nd:glass system was designed reasonably.Computation results indicate that the noise is compressed effectively,and the SNR is increased a lot.