Objective: To investigate the BMI distribution, obesity cognition, and weight loss behaviors of college students in a certain university, and explore the correlation between obesity cognition and weight loss behaviors, so as to provide a basis for college health education. Methods: A cross-sectional study was conducted by convenience sampling among 206 college students of different grades, genders, and majors. A self-designed questionnaire was used to collect data on basic information, obesity cognition, and weight loss behaviors. SPSS software was applied for statistical analysis, including chi-square tests and correlation analysis. Results: Among the 206 subjects, 51.46% (106 cases) had normal BMI, with 16.50% emaciated, 15.53% overweight, and 16.50% obese. Gender differences in BMI were significant: the male overweight rate was 27.91%, while the female obesity rate was 19.17% and emaciation rate was 25%. The overall rate of obesity cognitive bias was 42.72%, with a significant gender difference (χ² = 6.343, P = 0.042). Self-assessed weight was positively correlated with actual BMI (r = 0.372, P < 0.01) and obesity cognitive bias (r = 0.325, P < 0.01). Significant differences were found in weight loss methods among different obesity cognitive groups (χ² = 16.689, P = 0.034) and BMI groups (χ² = 26.514, P = 0.009). Knowledge accuracy varied significantly with obesity cognitive bias (χ² = 21.764, P = 0.001). Conclusion: College students in this university have prominent BMI abnormalities and widespread obesity cognitive bias, with insufficient nutritional knowledge and unscientific weight loss behaviors. Targeted gender-specific health education interventions are recommended to correct cognitive bias and establish healthy weight concepts.