Objective To study the body mass index (BMI) and living habits of 2018 freshmen in a university in Jiangsu Province, and analyze the influence of living habits on BMI, so as to provide the evidence for guiding college students to develop healthy living habits and good physical quality. Methods The freshmen were tested for the height and weight, and some of them were randomly selected to complete the habits questionnaire. Results A total of 350 freshmen completed the questionnaire, and 57.71% of them had normal BMI, 28.00% were underweight, 10.29% were overweight, and 4.00% were of obesity. The BMI of the boys was higher than that of the girls (P<0.001). The rate of overweight and the rate of obesity of the boys were higher than those of the girls (P<0.05), but the rate of underweight of the girls was higher than that of the boys (P<0.001). Among these freshmen who completed the questionnaire, 65.43% of them had a regular three-course diet and 69.14% had a weekly exercise habit. The rate of normal BMI of the regular diet group was significantly higher than that of the irregular diet group (P<0.05). The rate of normal BMI of the students who exercised 3 times or more per week was higher than that of other students (P<0.05). The overweight students had lower sleep satisfaction than other students (P<0.05). Conclusion The newly-acquired college students have underweight and overweight problems. The diet and exercise habits need to be improved. It is necessary to monitor the BMI of the college students and carry out the educations targeted to diet, sports and health, in order to promote the physical quality of college students.