BACKGROUND Risky sexual behaviour (RSB) drives the HIV and sexually transmitted infection (STI) epidemic among college students. Yet research on RSB remains limited among students with sexual experience in China. OBJECTIVE This study aims to determine the prevalence of RSBs and its correlates among students with sexual experience in Guangxi. METHODS A cross-sectional study was conducted among students with sexual experience from 14 colleges in Nanning City of Guangxi Province in 2021, using a convenience sampling method. Participants' sociodemographic characteristics, HIV/sexual health-related knowledge, sexual attitudes, sex education, behavioural characteristics, and HIV prevention service use were collected using a self-designed anonymous online questionnaire. A chi-square test was used to compare differences in the distribution of sexual characteristics and demographic information. Univariate analysis and logistic regression models were used to analyse the correlates of RSBs. RESULTS A total of 13,201 students completed the survey. It was found that 5.5% and 9.5% of participants reported having engaged in casual and commercial sex in the past year, respectively. Sexually experienced college students who were being single (adjusted odds ratio [aOR] 1.99, 95% CI 1.53–2.59), having higher number of sexual partners (aOR 2.08, 95% CI 1.34–3.23), having ever sought sexual partners online (aOR 8.29, 95% CI 5.94–11.57), having sex in the past year (aOR 8.40, 95%CI 5.65–12.50), having used psychotropic drug (aOR 5.91, 95% CI 3.28–10.63), and receiving AIDS education in the past year (aOR 2.79, 95% CI 1.81–4.29) were more likely to engage in casual sex. Being female sex (aOR 0.49, 95% CI 0.35–0.69), having sexual health-related knowledge (aOR 1.65, 95% CI 1.27–2.14), having ever sought sexual partners online (aOR 4.47, 95% CI 2.77–7.20; aOR 5.81,95% CI 4.2–8.04), and psychotropic drug use (aOR 17.72, 95% CI 11.37–27.62) were more likely to have commercial sexual behaviour. CONCLUSIONS The prevalence of casual sexual behaviour and commercial sexual behaviour was relatively high in sexually experienced students. This study highlights the need for a more targeted and effective inventions for college students, such as earlier and consecutive sex education, psychotropic drug use education, and HIV/STI prevention services, which should be implemented on campus to mitigate the RSBs that may contribute to HIV and STIs in this population.