BACKGROUND: Despite global efforts to control human immunodeficiency virus (HIV) among adolescents, the number of new infections among adolescents continues to increase. The increasingly widespread HIV epidemic among Chinese college students indicates an urgent need for more effective services in this context. To meet this need, we conducted a survey that aimed to produce a clear understanding of knowledge and sexual behavior concerning acquired immunodeficiency syndrome (AIDS) among college students. This study can serve as a reference for policy-makers and university administrators seeking to implement more targeted measures in this context. METHODS: In November 2024, a cross-sectional internet questionnaire survey was distributed at 13 universities in Guangzhou, China. The chi-square test was performed to examine the differences among respondents who exhibited different characteristics. A multivariate logistic regression analysis was conducted to explore the main influences on college students' AIDS knowledge. Confidence intervals that did not contain zero or values < 0.05 were considered to indicate statistical significance. RESULTS: A total of 12,632 valid questionnaires were collected. On this basis, a total of 11,587 (91.73%) students were determined to possess AIDS knowledge. The main influences on college students' AIDS knowledge were age, school classification, major, accommodation method, place of origin and average monthly living expenses. The proportion of students who reported a history of sexual behavior increased alongside students' grade. The relevant values were as follows: freshmen (5.16%), sophomores (11.9%), fourth-year and fifth-year students (15.59%), master's students (29.27%) and doctoral students (55.22%). A total of 6.63% of the respondents who had engaged in sexual behaviors reported that they had engaged in noncommercial sex with causal sexual partners. During the past year, the percentages of respondents who did not insist on using condoms during sexual activities with their casual sexual partners, male same-sex sexual partners, or commercial sexual partners were 30.58, 51.81, and 81.25%, respectively. The percentages of students who possessed AIDS knowledge and insisted on using condoms during sexual activities with "casual sexual partners (72.16%)" or "male same-sex sexual partners (48.19%)" were greater than the corresponding percentages of students who did not possess such knowledge ( < 0.01). Individuals who did not possess AIDS knowledge reported that they did not insist on using condoms during sexual activities with male same-sex sexual partners. "Did not buy a condom" was identified as the main reason for the failure to use condoms during sexual activities with casual sexual partners (26.43%) and commercial sexual partners on the basis of monetary transactions (48.00%). The main reason for failing to use condoms during same-sex sexual activities was "I did not think that it was necessary to use it" (41.67%). The percentage of college students included in the survey who reported that they had acquired AIDS knowledge from social software was the highest (76.96%). A total of 30.90% of the respondents reported that their favorite way of acquiring AIDS knowledge was through their school courses. CONCLUSION: The level of AIDS knowledge exhibited by college students is affected by various factors. Improvements in AIDS knowledge can help raise awareness of the need for self-protection during high-risk sexual activities among college students. The risk of contracting AIDS and other sexually transmitted diseases can be reduced through the use of condoms. Social networks are the main source by which college students acquire AIDS knowledge, although such students typically hope to acquire AIDS knowledge from their school courses.