The main purpose of this study is to explore the error types of junior high school students’ concepts of learning linear inequality and the most possible reasons leading to these errors.We hope this study would help implement remedial measures so that students can learn these concepts efficiently. This study adopts a quiz accompanying with interview. This study includes the effective samples of 72 students in the ninth grade of a public junior high school from Taipei City. The author collates the math final exam of the seventh grade in 2011 and chooses those which are about linear inequalities. After discussing with excellent colleagues, the author complies two copies of linear inequalities tests: one for the pre-test and the other for the post-test between which there is a week for remedial measures. According to the results of these tests, we statistically analyze the data and draw the conclusion of major error types which students often make, including changing inequalities、transposition error、the confusion of inequality expletive 、common denominator error and nature symbols、numbers in parentheses after going to change，etc. According to the result of the study, we compile proper remedial measures. Then we give a post-test to see how well the error types improve after remedial measures. We hope that this study can offer meaningful reference for junior high school math teachers when they teach the concepts of linear measures and when they compile test papers.