Abstract: The works of postmodern writer E.L.Doctorow are of strong ethic awareness. In The Waterworks， the author makes an ethic reflection upon the social issues of American Dream and takes rationalism which occupies the dominant position in culture and value orientation as a crucial reason for a series of moral problems. Under the revelation of Gnosticism， Doctorow explores the ideological similarities between Gnosticism and postmodern ethics and uses “gnosis” as moral knowledge to construct postmodern ethics. Ultimately， the author expects to use Gnosticism to define postmodern ethics as a universal morality so as to explore the possibility of the existence of moral truth.

Key words: Edgar Lawrence Doctorow, The Waterworks, gnosis, Gnosticism, postmodern ethics