Objective To determine the extent of off-label drug use in Pediatric Wards of West China Second University Hospital in 2010 and analyze its risk factors, so as to provide baseline data for getting acquainted with the extent of off-label drug use in pediatrics in China, and for making policies of off-label drug use. Methods The proportionate stratified random sampling was conducted to select medical advice and discharge medication for hospitalized children in Pediatric Wards in 2010. According to drug instructions, the off-label drug use of prescriptions of all selected children was analyzed in the following aspects, the category of off-label drug use, age, category of drugs and wards. In addition, a logistic regression was done that modeled the odds of receiving an off-label prescription as a function of the following possible risk factors: age, sex and the rank of doctors. Results The total 749 children were selected, and 14 374 prescriptions involving 385 drugs were analyzed. The rate of off-label drug use was 98.00%, 78.96% and 88.05% in children, prescriptions and drug categories, respectively. The main categories of off-label drug use were no pediatric information (29.41%), indication (18.35%), dosage (17.61%) and dosage range (±20%) (13.52%). The top 2 age groups of off-label drug use were adolescents (83.56%) and children (80.58%). The top 4 drugs of off-label use were those for alimentary tract and metabolism (82.28%), anti-infectives for systemic use (75.06%), blood and blood forming organs (79.27%) and respiratory (58.27%). The top 2 wards of off-label drug use were Pediatric Hematology (88.27%) and Neonates (79.12%). In hospital, children, adolescents and male patients had higher risk factors of off-label drug use, and doctors with senior rank prescribed more off-label prescriptions than those with intermediate rank. Conclusion The off-label drug use in Pediatric Wards is common in West China Second University Hospital. On the one hand, drug instructions lack the pediatric information, and, on the other hand, it’s badly in need of developing relevant legislations, regulations or guidelines to regulate off-label drug use, in order to avoid doctor’s professional risks and ensure the safety of pediatric drug use.