This paper approaches the variation features of normal reflection coefficients with frequency on the gas/water interface in a seismic frequency band and establishes the gas/water models of elastic porous medium by using the porous rock and porous fluid parameters from the Xinchang gas field and Denneman et al.(2002) model,respectively.Then,it discusses the simplified equations of normal reflection coefficients from Gurevich et al.(2004)and Silin and Goloshubin(2010),and calculates the normal reflection coefficients using the simplified equations and the built gas/water interface model and searches for the variation rule of normal reflection coefficients with frequency in a seismic frequency band.The results show that the method of asymptotic equation of Silin and Goloshubin(2010) can effectively indicate the variation of reflection coefficients with frequency on the gas/water interface in a seismic frequency band.