Symptoms of sexual behavior among learners has spread across the country. Data show that of 62 million adolescents in Indonesia, 21 million or 32% of whom have had sexual intercourse before marriage. In Indonesia, religion is still believed as one source to obtain moral values or behavioral norms. The absence of morals and religion is often accused of causing increased juvenile delinquency. This study aims to determine the relationship between adolescent sexual behavior with the level of knowledge of Islam. This research is correlational analytic with Cross Sectional approach. Independent variable in this study is the level of knowledge of Islam and the dependent variable of Sexual Behavior SMK Students. The population of this study are students of class X and XI SMK, amounting to 576 students. Sampling using probability sampling approach that is a number of 132 students. Analysis of research data using correlation calculation with Chi-square technique. The result of statistical analysis showed Pearson Chi-square value of 1.606a with Asymp. Sig. (2-sided) of 0.448 or greater than 0.05 means the correlation value is very weak, so the result there is no relationship between the two variables studied is the level of knowledge of Islam with sexual behavior Students SMK KH. Gholib Pringsewu.