The study aims to understand the status of concentration on extracurricular reading and the academic performance of junior high school students. The purposes are: 1. to know the status of concentration on extracurricular reading; 2. to analyze the difference of the variable between the factors of concentration on extracurricular reading and the academic performance; 3. to explore the relationship between concentration on extracurricular reading and the academic performance. Surveys were given to junior high school students at the 1th,2th and 3th grade respectively in the public schools of Kaohsiung; total 300 students have replied to the questionnaires from nine classes. Analysis of variance was applied to understand the internal factors, such as their motivation, interest and attitude upon concentrating on extracurricular reading and the external factors, such as attitude of parents and teachers as well as school promotion. How students concentrated on extracurricular reading and its relationship with the academic performance was explored. The conclusions were described as follows: I. Overall analysis of the current conditions shows that junior high school students have medium involvement in extra-curricular reading; their academic achievements are in the upper medium level. II. In terms of involvement in extra-curricular reading, female junior high school students outperform male junior high school students in their overall involvement in extra-curricular reading. Due to differences in the father¡¦s and mother¡¦s education levels and the mother¡¦s employment type, there are differences in perception, and perceptions are higher for junior high school students from middle-class families than from lower middle-class families. III. In terms of academic achievement, female junior high school students have greater perceptions for overall academic achievement than male junior high school students. Due to differences in the father¡¦s and mother¡¦s education levels and the parents¡¦ employment type, there are differences in perception, and perceptions are higher for junior high school students from middle-class families than from lower middle-class families. IV. Reading motivation, reading interest, parental attitudes, school promotions, reading attitudes, the degree of involvement in reading, reading achievements, and overall involvement in extra-curricular reading all have a significant effect on the overall academic achievement of junior high school students The conclusions can be used as reference for educational administration units, schools, teachers, parents and future researchers.