Abstract: A new method based on well logging data and pre-stack seismic inversion parameters, which is called pore bulk modulus method, is presented to quantitatively calculate pore fluid saturation. This method is based on Gassmann equation. It is assumed that the lithology is predicted credibly and the shale content and porosity are calculated accurately as well. Then the dry rock bulk modulus and pore space modulus are calculated from well logging data. Finally, the relation equation between water saturation and pore bulk modulus is constructed by using multiple-regression scheme fitting dry rock modulus from elastic parameters obtained from various pre-stack inversion methods, to quantitatively calculate fluid saturation. Actual seismic data from SLG region of Changaing oil field is used to verify the method. The result shows that this method can be used to quantitatively predict gas saturation and to semi-quantitatively predict flow potential. High gas rate wells are successfully drilled in terms of the prediction results.