The study aims to analyze the difference of physical fitness of all grades of students of Liuhsin Senior High School, hoping to establish a reference for the physical education and activities. The study included 213 students (126 males and 87 females) enrolled at the school in 2018 as subjects, conducting the test by the method established by MOE, and analyzing the physical fitness test results by the method of descriptive statistics and ANOVA. The study points out that the significant physical fitness performance difference among all grades of the students is the result of one-minute sit up and grade 1 students are those with worst performance. Therefore, it's critical to improve the abdominal muscles and muscular endurance of the grade 1 students and it's suggesting that related course shall be arranged for the students to enhance their physical fitness.