The purpose of this study is to understand the important experiences of low-achievement students in the learning process and to explore the impact of these important learning experiences on their academic achievement motivations, and to clarify the relevant factors that influence their motivation. In order to achieve the above research purposes, case study was used in the research, and six low-achievement students were used as research cases. Methods for collecting data included natural observation, interviews, and document analysis for a period of one semester. Through this study, it is found that the factors affecting the achievement motivation of the students with low achievement are the teacher-student relationship, parental attitude, experiences of success or failure, the possibility of success, and social reinforcement. In the research suggestion, this study proposes five suggestions for improving the achievement motivation of low-achievement students for reference by other teachers and researchers.