This research investigates the strategy for application of E-Trade to SMEs to analyze the economic effect of e-trade. And the influence of the proliferation of e-business and e-trade upon the industrial business conditions, value-chain, and business activities is also analyzed. The subjects of the inquiry are the nationwide petrochemical industries in which small and medium sized companies are in mutual and intimate cooperation. The results show that the business structure of the petrochemical industries are divided into four stages, and, with the introduction of e-business, the value chain is changed by stages. And the change of value-chain explains the transition of the e-business of petrochemical industries including trade business into industrial DB and leads to a variety of the economic effect including the reduction in the trade expense, the change of the production process, and the innovation of trade structure.