Objective: To explore the long term trend of forced vital capacity to weight index (FWI) among Chinese Han students aged 7-18 from 2000 to 2019, and to predict its changes over the next decade, so as to provide scientific evidences for targeted health interventions and school health policies. Methods: Based on the data of the five Chinese National Surveys on Students Constitution and Health conducted from 2000 to 2019, a total of 216 500, 233 565, 215 267, 214 256 and 212 632 Han students aged 7-18 were included, respectively. The long term trend of FWI among students was analyzed, and the GM (1,1) grey model was used to predict FWI changes over the next decade. Subgroup analyses were conducted by sex, age, and urban-rural residence. Results: The FWI levels of Chinese Han students aged 7-18 were (55.30±11.47)(47.43±11.92)(48.11±12.46)(48.75±12.81)(50.93±13.11)mL/kg in 2000, 2005, 2010, 2014, and 2019, respectively. The FWI of Chinese Han students showed a decreasing then increasing trend from 2000 to 2019, reaching the lowest point of approximately 47.03 mL/kg around 2006, and was projected to recover to 52.88 mL/kg by 2029. Boys had higher FWI for each year and the total level than girls from 2000 to 2019( t =72.58-304.66), and the decline between 2000 and 2005 was smaller in boys (13.1%) than in girls (15.4%). However, the gender gap gradually narrowed and was projected to reduce to 5.36 mL/kg by 2029. FWI increased with age, with the largest difference observed in 2014 between the 7-9 and 16-18 age groups (8.62 mL/kg). Before 2014, urban boys had slightly lower FWI than rural boys; the gap narrowed thereafter, and their FWI levels were expected to become similar by 2029. Urban girls generally had higher FWI than rural girls, and the urban-rural gap showed an increasing trend. By 2029, the largest difference was projected to occur in the 13-15 age group, reaching 7.74 mL/kg. Conclusions The FWI of Chinese Han students showed a trend of initial decline followed by a gradual increase from 2000 to 2019, with notable differences across sex, age, and urban-rural residence. Greater attention should be paid to the respiratory health of rural girls, and effective measures should be taken to reduce urban-rural disparities.