Hadiths are not sacred texts as the Koran. However, the hadith is always the second reference after the Koran and occupies an important position in Islamic studies. Considering the writing of the hadith which was carried out hundreds of years after the Prophet Muhammad died, many opinions were crossed over the validity of a hadith. so that this raises some groups to doubt and deny the truth of the hadith as a source of law. This paper will focus on discussing the study of the determination of the validity of hadith as a source of law according to Imam Syafii. This paper uses the library research method with the study of text analysis, therefore the author refers directly to the books written by Imam Shafi'i and makes comparisons with books ...