Objective: To understand the current situation of sedentary behaviors among middle school students and its relationship with physical health. Methods: Data came from the Taizhou City and Township Health Survey in 2018. Sedentary behaviors and physical fitness of 2 374 middle school students in Taizhou were analyzed. Results: The total time spent in sedentary behaviors of middle school students in Taizhou was (8.75±1.56) h/d on weekday and (7.34±1.55) h/d on weekend; Compared with students whose screen time <2 h/d in weekday or weekend, weekend homework time <2 h/d and private tutoring class <2 h/d, students whose screen time ≥2 h/d in weekday or weekend, weekend homework ≥2 h/d and private tutoring class ≥2 h/d showed higher rate of low physical fitness(OR was 1.43, 1.37, 1.12, 1.43, respectively, P<0.05). Conclusion Long duration of weekend homework and private tutoring class, as well as high screen time in weekday and weekend is associated with decline of physical fitness among middle school students.