Background: Numerous studies have been carried out to identify the factors influencing the choice of field of study for ninth grade students. But in the field of qualitative research and the role of childhood in selecting the field of study, there is a vacuum in the context of the country. Aims: The purpose of this study was to Qualitative Study of the Role of Pre-school and Elementary School periods on Field Selection of educational for ninth grade students. Method: This study was a qualitative and data-based theory. The statistical population consisted of The ninth grade students one of the schools in district 2 of Tehran city were academic year1395-96, 16 were selected by theoretical sampling method. The data were collected through semi-structured and in-depth interviews. Data analysis was performed by method of Strauss and Corbin (1998). Results: Factors obtained in the pre-school period include pursuing interests and abilities and preparing the environment for the emergence of one's interests and abilities. In the elementary school period, the content factors include individuals’ experiences and relatives’ behavioral reactions, and in the section of the process factors associated with this period, the axial codes were observe and modeling (influence of others) and internalization. Conclusions: In the pre-school period, families and relatives are effective in creating and pursuing one's desires and abilities, during elementary school due to increasing age and more complex cognitive processes, as well as school entry. Factors are becoming more diverse.