When we talk about grammar we mean some main rules that with using them the computer will be able to parse a sentence. For Persian language, extracting grammatical rules has been done for the first time. Our designed grammar contains about 200 rules which are extracted based on GPSG grammatical model. This grammar can parse many of Persian written sentences. Extracting grammatical rules which can parse all types of sentences in a language is a difficult, time consuming and dynamic work. So the grammatical rules are being developed now. Besides extracting general rules, it is possible to extract special rules for some special purposes. Persian grammatical rules can be used in speech recognition systems, sentence structural correcting systems, machine translation and other related systems.