Religious laws that are related to human duty are called Sharia laws. Shariah rulers are obtained with the help of knowledge such as Darayah, Rijal, principles of jurisprudence and jurisprudence. The jurists refer to four sources for deriving Sharia rulings: the Qur'an, the Sunnah, common sense, and consensus, which they call Arba'ah arguments. In order to improve jurisprudence, the principles must be strengthened, and in order to strengthen the principles, it is necessary to strengthen the role and place of reason in the principles of jurisprudence. The important discussion in the principles of jurisprudence is the validity of reason in deriving branches; That means, can reason be considered as a source of inference along with the book and Sunnah, or does it not have this ability and position? In this regard, this research first studies the concept of reason and the place of reason in the principles of jurisprudence. Then it deals with the application of reason in the principles of jurisprudence and the inference of Sharia rulings. In the end, it examines the validity of reason and the ability to infer religious rulings and the opinions of supporters and opponents of reason. The research method in this research is descriptive-analytical, the required information is cited through library studies, the goals of this research are to explain the concept of reason and the place of reason in the principles of jurisprudence.