Background This study describes road traffic injuries among school-aged children in Guangzhou, China, and examines the effect of road safety knowledge and risk behaviours on road traffic injuries. Methods A stratified cluster sample of 3747 children from six primary schools and six middle schools in Guangzhou, China, was surveyed. Data were collected on sociodemographic factors and road traffic injuries during the past year. Knowledge about road safety rules was assessed using a 14-item road safety knowledge index, and risky road safety behaviours were measured using a 25-item road safety behaviour index. Results A total of 403 (10.8%) students reported having at least one road traffic injury during the past 12 months. A high proportion of injuries was found among children who were boys, in primary school and from the suburbs. Bicycle-related injuries were the most common (46.0% of all injuries). Motor vehicle-related injuries had higher hospitalisation rates and worse psychological impact than bicycle or pedestrian injuries. Children with low and medium road safety knowledge had 1.5 to 3 times the odds of injury compared with students with high road safety knowledge. Students with high scores on the risky road behaviour index had twice the odds of injury (OR 2.04, 95% CI 1.47 to 2.84) compared with students with low scores. Conclusion Better road safety knowledge and the avoidance of walking or cycling-related risk behaviours are protective factors for road traffic injuries among Chinese school children. More injury prevention programmes are needed to improve road safety knowledge and reduce risk behaviours.