The purpose of this study is to analyse factors related to sex behavior and intention to premarital purity on the basis of theory of reasoned action. A structured Questionnaire was developed on the basis of Triandis model. Survey was conducted to 1662 unmarried person in high school students, college students, and workers. The results are as follows. For the factor of sexual behavior, male, older age had higher experience to sexual relationship, but for the factor of premarital purity, female and workers than student had higher consciousness of purity. Positive attitude to premarital purity, expectation toward preservation of purity, parental and social normative influence and facilitating factor such as experiences of sex education showed significant relationship to intention of premarital purity. Also multiple logistic regression showed that health behaviors such as smoking and drinking, sex and job were statistically significant factor for sex behavior. The result of this study suggest that educational program sex as well as good health behavior should developed and theory-based models in conducting health education research.