The aims of this research were: 1) to know the students competence in using comparative sentence. 2) to find out some errors made by students in using comparative sentence. The method of this research was descriptive quantitative. The population of this research was the second grade students of MAN Purwokerto 2 in the school year 2009/2010, consisting of 237 students from eight classes. The writer took 15% of the population as the sample. The total number of the sample in this research was 35 students. The writer has taken the students of each class randomly. The data was analyzed by using descriptive statistic. After analyzing the data, it was revealed that the mean of students’ competence in using comparative sentence was 58,4% so it belongs to fair category. It was revealed that the error made by students in using comparative sentence were false concepts hypothesized because the students still difficulties in using comparative sentence.