The objectives of this study is to find out the correlation on (1) students’ grammatical competence and writing skill; (2) students’ writing interest and writing skill; and 3) students’ grammatical competence and students’ writing interest simultaneously and writing skill.

This study used correlational method with quantitative approach. The population was all the eighth grade students of MTs Negeri 2 Surakarta. This study involved 32 students that were selected by using cluster random sampling. In collecting the data the researcher used questionnaire and test. The techniques which were used of analyzing the data were Correlation and Regression both of simple and multiple. The result of the research show that (1) there is a positive correlation between grammatical competence and writing skill (rx1y = 0.368); (2) there is a positive correlation between students’ writing interest and writing skill (rx2y = 0.430); (3) there is a positive correlation between students’ grammatical competence and, writing interest and writing skill (R = 0.663). The students’ grammatical competence gives 24.68?fective contribution to writing skill and the students’ writing interest gives 19.32?fective contribution to writing skill. Both students’ grammatical competence and writing interest give 44?fective contribution to writing skill. It means that the increase of students’ grammatical competence and writing interest simultaneously will be followed by the increase of students’ writing skill. Based on the study, it can be concluded that students’ grammatical competence and writing interest are aspects that support writing skill.