Abstract: Taking Sulige gasfield as instance, the relation between elastic parameters and gas reservoir has been discussed in detail in this paper. The research results include: Lam constant ( ), shear modulus ( ) and mass density ( ) all bear relation to lithology and porosity , and decrease with porosity increasing when lithology doesn't vary. The decreasing grade of is largest, next is , and is hardly affected when porewas filled with fluid. the ratios of / and vp/vs decrease when pore was filled with gas or oil, and / decrease more rapidly than vp/vs . But the ratios increase when pore was filled with water. / gas saturation relation is nonlinear and relate to porosity. But / porosity relation is hardlyaffected by saturation. Sowe can estimate porosity by using / then saturation by using / Based on the rock physical theory of fluid saturated porous media, the elastic parameter-porosity relation and elastic parameter-saturation relation have been build in the study area. Combining with prestack inversion and Paisson's ratio from the inverse elastic parameters, it can be used to predict the distributions of lithology and gas and estimate the porosity and saturation. The later drilling testified the reliability of the estimated results

Key words: elastic parameter, lithologic oil-gas reservoir, prestack inversion, porosity, saturation