Abstract: The Huagang Fm.reservoir in Structure A in Xihu sag is characterized by deep burial depth,with low porosity and low permeability,and quick lateral variation.By analyzing the petrophysics of low permeability gas layers in drilled wells,the relationship between elastic parameter with lithology,and physical property with oil-gas bearing conditions has been studied.The parameter of Vp/Vs has been selected as the sensitive parameter to identify low-permeability gas reservoir,and pre-stack inversion has been conducted for the structural area.Combining with lithologic inversion of Vp/Vs and results of structural interpretation,the boundary of low permeability gas reservoir has been determinate,and a set of effective technology has been established for identification of the boundary of the low permeability gas reservoir.