In this paper, a directed and weighted world crude oil trade network is constructed. Based on the built network, we apply top network method and modified closed-system input-output method to assess the relative importance of countries in the international oil trade. The top 1 network consisting of top trade relations, can well reflect countries' preference in choosing oil trade partners. As a simplified network model of international oil trade network, the top 1 network has been analyzed the structure and evolution. In order to identify important oil trading countries, the modified closed-system inputoutput analysis has yielded some promising results, which show countries who play key role in international oil trade, are trading large oil volumes. In addition, by describing the influences of countries on each other, we find major oil importers have a much effect on other countries, including major oil exporters. The evolution analysis obtained by these two methods coincide with each other. To conclude, some suggestions are given according to the results. (C) 2016 Elsevier Ltd. All rights reserved.