Eugene O’ Neill, an American playwright, is very interested in Chinese Taoism. In many of his middle and late works, we can see the profound influence of Taoism on him. Taking Marco Millions, O’Neill’s mid-term masterpiece as an example, this paper analyzes Taoist thoughts such as Unity of Opposites, Circulation and Reversion, Non-action and Unity of Body and Soul contained in this play by means of text analysis. Through the analysis, we can see that O’ Neill tried to find a new way of spiritual sustenance in the eastern Taoist thought to get rid of the disadvantages of western material civilization.