The purpose of the study was to explore the relation of the adolescents’ leisure activity participation and premarital sexual behavior. The study aimed at senior/vocational high school students in Taipei City for subjects and the information obtained from the 888 students by quota sampling was analyzed. The research tools consisted of three sections: "Personal Background Survey", "Leisure Activity Participation Scale" and "Premarital Sexual Behavior Survey". The statistical methods included descriptive statistics, t-test, one-way ANOVA, Pearson correlation and multiple regression analysis. The major research results are as follows:1. Adolescents' "leisure activity participation" tends to be at the medium-low level. 2. Adolescents' "premarital sexual behavior" tends to be "infrequent and conservative". 3. There is a significant difference between "leisure activity participation" and "monthly allowance"; and between "leisure activity participation" and "main companions of leisure activity participation". 4. There is a significant difference between “premarital sexual behavior" and the variables: gender, family style, parenting style, and monthly allowance. 5. There is a significant positive low correlation between "leisure activity participation" and "premarital sexual behavior" for the adolescents.According to the above results, we suggest that by participating more in outdoor activities and proper leisure activities and learning accurate sex and love concepts, the adolescents' sexual desire and impulse could be diversified and the possibility of their premarital sexual behavior might be reduced.