In order to better understand what is known as the „Septuagint Canon”, it is important to know the process of formation of the Hebrew Bible canon and the adaptation of the LXX by early Christians as the sacred text. According to the research conducted over the previous decades, we will present in this article the following four points: 1) the terminology currently used to designate the books contained in the OT canon; 2) the main steps of formation and stabilization of the Jewish Canon; 3) the constitution of the Greek OT corpus; and in conclusion 4) the LXX in the Church over the first four centuries.