Whit the beginning of the great absence period, the literature used in the science of theology gradually changed and the lmami theologians turned to a rational and philosophical approach to explain the theological and religious teachings, according to varios philosophical and intellectual rules, concepts, terms and arguments. Until that time, it was not paid much attention and religios doctrines were usually proven and investigated by means of narration and according to auditory evidence. In this article, in order to know more accurately and precisely the process of entering rational and philosophical topics into theology, or in other words, the approach of philosophical theology, the role of sheikh mofid and abu ishag nobakhti in the beginning and formation of this trend, in the form of six axes that they are: existence (latif al-kalam), in which issues such as: definition and divisions of science, definition of existence and non-existence, division of existence and its properties, essence and breadth. Theology, in wich issues such as: proving the necessity of existence and explaining his positive and negative attributes. Justice, in which issues such as: proving that one is just and wise is obligatory, and good and bad are intellectual. Guidance (prophethood and imamate), which also includes things such as: the necessity of prophethood and imamate, the necessity of infallibility and the superiority of the prophet and imam. Apocalypse, in which the issues are: proving the necessity of resurrection, proving the path, the measure, the punishment of the grave and its watcher, according to the mentioned approach and whit the analytical and descriptive method and based on library studies and the review of the works in theological books. They have been discussed and investigated and finally the effects and function of this trend and approach whill be revealed in the works and thoughts of these two thinkers.