Combining the concrete cases of EC Commission and the Court of Justice of the European Communities, this paper analyzes the key article of EC competition law, and makes a deep inquiry into the issues such as what is"abuse by undertaking of a dominant position", what is"affect trade between Member States" and what is the formality of"abuse of a dominant position".

The United States and EU,with advanced anti-monopoly legislations,have comparatively matured experiences in regulating the abuse of a dominant position.

Prohibition of abuse of dominant position is one of three important pillars of anti-monopoly law.

According to anti-monopoly law,monopolistic behaviors are composed of three parts such as merger of enterprises,conspiracy of enterprises,and abuse of dominant position.

The abuse of dominant position causes great injury to market competition, so there is a remarkable significance to carry out a theoretical research in both the legislation area and the judicial practice area in anti-monopoly field.

With price discrimination, exclusive Transaction, tied sale, dumping with low price, and monopoly with long price, the abuse of dominant market position of multinational corporations in China awfully injured the legal rights of Chinese consumers and operators; and disturbed the competition order of our country seriously.

The main purpose of this article is to avoid the abuse of dominant market position, preserve rational market structure, protect equitable competition and the legal rights and interests, promote and guarantee the healthy development of market economy.