BackgroundBody shape and fitness (BSF) is critical for overall well-being, while university students in China are subjected to stress, peer pressure, performance anxiety, busy schedules, and lack of sleep, which can easily lead to poor BSF. This study aimed to explore the knowledge, attitude, and practice of BSF and related factors among university students in China.MethodsThis web-based cross-sectional study was conducted on students of 15 universities in China between September 1st and November 30th, 2022. The KAP scores were evaluated using a 38-item questionnaire, including social demography, knowledge, attitude, and practice. Univariable and multivariable regression analyses were performed to identify the factors associated with KAP.ResultsA total of 995 valid questionnaires were collected. There were 431 (43.3%) males and 564 (56.7%) females. Most participants were sophomores (51.2%) and freshmen (36.3%). Most participants had a BMI of 18–24 kg/m2(66.1%). The students scored highly on BSF-related knowledge (8.30 ± 1.49), moderately on attitude (37.20 ± 4.46), and low on practice (19.64 ± 4.62). Multivariate logistic regression analysis showed that attitude score (P= 0.001), sex (P= 0.001), grade (P= 0.011), body mass index (BMI) (P< 0.050), parent’s education level (P= 0.005), monthly allowance (P< 0.050), and sleep quality and habits (P= 0.016) were independently associated with practice scores.ConclusionsUniversity students in China were found to have good knowledge, moderate attitude, and poor practice toward BSF. Attitude, sex, grade, BMI, parents’ education, monthly living expenses, and sleep quality and habits affected their practice. More BSF-related courses or activities are required to motivate students, especially females.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12889-023-16122-8.