In Sulige area，when gas saturation is lower than 70%, the change of Poisson's ratio is not obvious, and the application of AVO technique to detecting gas potential does not yield satisfactory result. The elastic impedance method based on Fatti approximation uses prestack data for inversion and includes abundant lithologic and fluid information. Nevertheless, its shortcomings in the aspects of the unstable solution in small angles and the low inversion precision built in wet rock background are also very obvious. The improved Fatti approximation formula is more stable, and its inversion precision built in the known regional rock property relationships between variables for the background case is raised. Practice demonstrates that the application of the crossplot of LambdaMuRho attributes extracted from the elastic impedance inversion volume is very effective in low gas saturation detection in Sulige area，as evidenced by the clear reflection of the reservoir information.