Background: Deviations attitudes and sexual action in teenagers occurs because of lack of knowledge of reproductive health. This is shown by the increase in premarital sexual attitudes and action in adolescents in many cities. Reproductive health knowledge is needed by teenagers as a preventive and promotive efforts in forming the moral adolescents. Objective: Knowing the relationship between the level of reproductive health knowledge with premarital sexual attitudes and action in college students. Methods: This research used an observational cross sectional design. The instrument to measure the level of reproductive health knowledge with premarital sexual attitudes and action is a quesionnaire. The subjects were Muhammadiyah University college student class of 2013 to 2015, 389 students in amount. Results: Analysis of data used Spearman Rho correlation. Spearman Rho correlation showed that there was significant correlation between the level of reproduction health knowledge and premarital sexual attitudes with the value of correlation coefficient (r) = +0,119 and P = 0,019 (P<0,05). There was not significant correlation between the level of reproduction health knowledge and premarital sexual action with the value of correlation coefficient P = 0,123 (P>0,05). Conclusions: there was relation between the level of reproduction health knowledge with premarital sexual attitudes and that there was no relation between the level of reproduction health knowledge and premarital sexual action.