Abstract: Seismic velocity in sediment will increase when gas hydrate occurs, and the impedance of the sediment is greatly different form surrounding sediments. Therefore, seismic impedance inversion technology, which may identify the difference between the sediments with and without gas hydrate, is used to predict the distribution of natural gas hydrate. Since logging data have high vertical resolution and seismic data have high lateral resolution, accurate spatial distribution of gas hydrate can be obtained by joint inversion of well data and seismic data. The gas hydrate reservoir in Shenhu sea area, northern South China Sea, was characterized by such well-seismic inversion technology. The study shows that the gas hydrate reservoir in the area is characterized by high impedance, ranging between 3450-4500m/s*g/cm³. At the same time, the petrophysical templates for porosity and saturation prediction was established according to the effective medium model. The predicted porosity and saturation data of gas hydrate reservoir are in good agreement with the log interpretation results, which provides more accurate physical property data for calculation of gas hydrate reserves.