The ideas of postmodernism profoundly influence both theories and practice models of social work since 1980s. This article mainly focuses on the discussions of impact of postmodernism on social work profession and interprets those new changes related to the paradigm of theories and practice models in the field. The author argues that，as a philosophical discourse and thinking mode，postmodernism not only challenges traditional social work theoretical assumptions and practical approaches，but also raises a series of daringly valuable questions regarding social work development as a profession in the developing countries. The author concludes that the core value of postmodernism for social work is its proposal of a necessary linkage between ethical reflection and practical rationality.