Abstract: Conventional reservoir evaluation method and its existing problems are analyzed through studying commercial GIS. The spatial database of oil-gas reservoir evaluation is established. All kinds of multidisciplinary oilfield graphic information and its correlating attribute data relating to reservoir are integrated. By means of integrating reservoir evaluation model with GIS, oil-gas reservoir evaluation problem is figured out. Thus the spatial analysis function of GIS is extended. An instance of a western oilfield in our country is cited to prove that the new method makes the evaluation more accurate and reliable.