Objective: To explore the temporal variation in physical health status among college students, analyze the correlation and dose response relationship between body mass index (BMI) and physical fitness indicators, so as to provide a scientific basis for physical health intervention among college students in universities. Methods: A total of 4 910 freshmen in the 2021 grade at Xi an Jiaotong University were selected. The BMI and changes in five physical fitness indicators (50 meter run, endurance run, standing long jump, sit and reach, and pull up or 1 minute sit up) were continuously assessed during follow up evaluations from 2021 to 2024. One way analysis of variance, generalized estimating equation (GEE), and other statistical methods were used to analyze the trends in temporal variation among the physical fitness indicators as well as the correlation characteristics and dose response relationship between BMI and physical fitness. Results: In 2021 the overweight and obesity rates among male freshmen were 20.36 % and 8.62%, respectively, and 12.91% and 2.91% among female freshman, respectively. From 2021 to 2024 the BMI of male and female students showed an upward trend with a significant increase( F =87.29,3.69,both P <0.05). The physical fitness indicators for both male and female students, including the 50 meter run, standing long jump, pull up and 1 minute sit up, first increased and then decreased, the endurance run performance decreased, and the sit and reach performance first decreased and then increased. The GEE model showed that BMI was negatively correlated with the performance of standing long jump, pullup/1 minute sit up, and sit and reach in both male and female students（ β =-1.72，-0.34，-0.15；-0.94，-0.26，-0.12）, and positively correlated with the time of 50 meter run and endurance run（ β =0.05，3.16；0.03，1.86）（all P ＜0.05）. The increase in BMI was associated with physical fitness decline in a non linear dose response relationship, while the sit and reach performance reached a peak at a BMI of approximately 22 kg/m 2, then decreased with the further increase in BMI. Conclusions A significant negative correlation is demonstrated between BMI and physical fitness indicators and male students are more sensitive to changes in BMI. College students should be guided to actively manage their weight and attach importance to physical exercise to improve their physical health.