The purposes of this study are to develop mathematics-grounding teaching materials of one-variable linear equation remedial instruction for seventh graders and to investigate the related implementation process and learning effects. This study has adopted an action research method. The mathematics-grounding teaching materials were designed according to the grade specifications of one-variable linear equation and the remedial instruction were implemented on seven underachievers. During the remedial instruction, classroom observations, quizzes and interviews were used to determine the performances of the students and to modify the curriculum and instruction accordingly to improve the students' performances. The research results show that the remedial curriculum did improve the learning effects of underachieving students regarding one-variable linear equation, and the remedial curriculum did increase students' interest level. There were some limitations on such instructional design. However, the PPT animation materials can help to improve the learning effects of word problems solving.