杜牧对牛李两党的态度，前人有“恩牛怨李”和“党牛怨李”两说。杜牧怨恨李德裕，是因为他在会昌二年（842）遭到李德裕的遣逐，被迫由比部员外郎移任黄州刺史．本文从杜牧与牛僧孺的密切交往、杜与李德裕的政治矛盾、杜牧与李德裕道德意识上的差异三个方面，探讨杜牧遭遣的主要原因． Du Mu’s attitude toward the Niu-Li and Bipintilla parties had two previous statements of “mercy and indignation” and “party resentment and malice Lee.” Du Mu resentful Li Deyu, because he was Huichang two years (842) was Li Deyu’s deportation, was forced to be replaced by the Department of foreign Lang Huang provincial governor. This article discusses the main reasons for the removal of Du Mu from three aspects: the close contact between Du Mu and Niu Seng, the political contradictions between Du and Li Deyu, and the moral awareness differences between Du Mu and Li Deyu.