The purpose of present study is to explain the concept of shadow curriculum in educational system of Iran. This study used qualitative method., the meaning of shadow in various fields of The science such as economics, politics, music, etc. have been investigated. its common characteristics were explained by Using meta-synthesis. In the next phase of the research, the views and theories of sociology, political and philosophical sciences related to the field of education are studied and to increase the conceptual richness of the research, and a better explanation of the conceptual framework for the shadow curriculum, with 8 experts in this field Interviews were conducted. Of these, three main themes are namely, why, how and what the concept of shadow or underground curriculum. The interview format was analyzed by thematic analysis method. according to results of the study, the main attribute of the shadow is Conflict with its reference. Accordingly, the the shadow curriculum can be defined as a set of activities that are performed by students, teachers, and administrators, and. . . in schools that are in contravention of the formal curriculum. In other words, shadow curriculum, is learning that is practiced, although not officially recognized as legitimate by the Official curriculum, but students and teachers defend it.