"The purpose of the present study was to explore the changes of mathematic self-efficacy of high school students who participated in the remedial instructions of mathematics based on the framework of self-efficacy （Bandura, 1997）. Self-efficacy refers to the belief of the attainability toward certain goal one perceives, which will affect the level of effort and the achievement as a result. Data of semi-structured interviews and the records of the reflection of the researcher had been collected and analyzed. The results showed that most of the mathematic low achievers refused to participated in the remedial instructions because of their low self-efficacy due long-term failures in mathematics. In the remedial instruction, teachers would give easier materials to adapt to students' ability, which provided students successful experience in learning mathematics. In addition, teachers would provide social or material reinforcements to reinforce the sense of success, which would enhance students' feeling of self-efficacy in mathematic remedial instruction. However, the feeling of self-efficacy couldn't be transferred to general mathematic classes. Suggestions of remedial instructions and follow-up studies has been provided based on the results."