Linguistic deviation occurs a lot in Arabic language. In some uses, it occurs either compulsory or non-compulsory.The current study aims at exploring both types of linguistic diversions (compulsory and non-compulsory) in the poetic work of Imam Shafi'i. It also discusses the phonetic, grammar and structure deviation and their effect on the beauty of the poetic structure and on the way of informing, surprising and attracting the audience.