Amplitude versus offset analysis is a conventional seismic exploration technique in geophysical and lithological interpretation and has been widely used in onshore and offshore exploration. Its use in marine gas hydrates research is still in initial stages. In this study, AVO analysis is applied to seismic profiles tied to a couple of drilling sites in the northern slope of the South China Sea where hydrate samples have already been recovered. The AVO responses of free gas, bottom simulating reflectors (BSRs), and gas hydrates were discussed, and the AVO attributes in relation to gas hydrates were summarized. The changes of intercept, gradient, fluid factor and Poisson’s ratio clearly showed the location of free gas and the BSRs, and spatial relations between blank zone, BSR, gas hydrates and free gas.