Abstract: Objective：To investigate the characteristics of concept, cognition and behavior of sexual and reproductive health in those unmarried migrant adolescents in China, so as to make some reasonable suggestions for improving the health services for those people. Methods：One hundred and twenty unmarried migrant adolescents in six provinces of China were interviewed with a qualitative questionnaire form. The qualitative analysis was based on the data of the characteristics of concept, cognition and behavior of sexual and reproductive health in those people. Results：Those unmarried migrant adolescents had multiple sexual concepts. They got knowledge on sexual and reproductive health from internet, books/magazines and friends, but their knowledge level was fairly limited. A lot of unmarried migrant adolescents had sexual experience; however, their cognition of sexual self-protection was poor. Conclusions：The characteristics of sexual knowledge, behavior and morality in those unmarried migrant adolescents are profoundly affected by their upbringing background, education, work environment and mobility, which is related to the widespread but serious problems of sexual and reproductive health in those people. It is necessary to improve the quality of public services of sexual and reproductive health in those unmarried migrant adolescents by providing easy ways to obtain contraceptive devices，enhancing sexual and reproductive health education in school, and providing public services specifically for those people.

Key words: Adolescent, Health knowledge, attitudes, practice, Sexual behavior, Reproductive health services