Abstract: Part-Of-Speech (POS) tagging is essential work for many models and methods in other areas in natural language processing such as machine translation, spell checker, text-to-speech, automatic speech recognition, etc. So far, high accurate POS taggers have been created in many languages. In this paper, we focus on POS tagging in the Persian language. Because of problems in Persian POS tagging, a comprehensive plan is proposed to reach a high efficient POS tagger in this language. Afterward, morphological analysis is investigated in Persian and it is shown that using a morphological analyzer in inflection level, POS tagging has been improved greatly. The results describe the fruitfulness of the proposed method.