Objective: To examine the relationship between 24 hour movement behavior and physical fitness of pupils by using compositional analyses, so as to provide a theoretical basis for physical activity promotion and physical fitness improvement. Methods: By random cluster sampling method, 120 students of grade 4 and 5 from the Second Experimental Primary School of Yingze District of Taiyuan were selected. Physical fitness was evaluated by the indicators of the Protocol of National Physical Training Standard and 20 meter shuttle run. The movement behavior was measured by accelerometer. The relationship between each behavior and physical fitness was analysed by component multiple linear regression, and the effect of replacement of components on physical fitness was discussed. Results: Girls 1minute situps were lower than boys（24.79±7.77，28.21±6.52），and sitting forward flexion was higher than boys[9.00（5.00，14.00），5.20（1.00，9.75）cm]（ t/Z =2.60，-3.15， P ＜0.05）. Boys showed higher light physical activity(LPA), moderate to vigorous physical activity(MVPA) and lower sedentary behavior(SB), while girls showed lower LPA, MVPA and higher SB. MVPA was positively correlated with the performance of 30 second rope skipping and 20 meter shuttle run ( β= 13.19, 7.90, P <0.05). Sleep(SLP), SB, and LPA were not significantly correlated with physical fitness. After re allocating 10 min MVPA to SB and SLP，the performance of 30 second rope skipping and 20 meter shuttle run increased by 2.25，2.28 and 1.28 ,1.34 times，respectively，while significantly decreased after reverse reallocation ( P <0.05). MVPA replaced LPA，the 20 meter shuttle run performance increased 1.46 times，while decreased significantly in reverses ( P <0.05). Conclusion MVPA is positively correlated with the speed and endurance of pupils. There are gender differences in movement behavior patterns and physical fitness. Children, especially girls, should be encouraged to raise exercise awareness and increase PA, especially MVPA.