Nurses play a key role in administering sedation to mechanically ventilated children, which impacts children's psychological, physiological and cognitive changes in the paediatric intensive care unit. This study aimed to survey the sedation practices of paediatric intensive care unit nurses on mechanically ventilated children in China and explored the influencing factors. A cross‐sectional survey was conducted based on electronic questionnaires comprised of the Nurse Sedation Practices Scale (Chinese version) in 14 different types of paediatric intensive care units of 11 academic hospitals in China from 15 February to 15 April 2017. A convenience sample of 495 nurses [73·4% response rate, (674)] completed the survey. Seven units applied Ramsay Sedation Scale as a sedative assessment tool. The majority of the nurses used observed behaviours and physiological changes of the ventilated children as indicators to assess the sedation level, and they had a positive attitude and intention, which may influence practice positively, whereas high clinical workload and the lack of communication between the nurses and families might hinder practice. The practice of sedation varied greatly in different regions, and the respondents of the northwest region scored lower. Paediatric nurses in China rarely used a validated paediatric instrument to assess sedation, and most nurses relied on physiological and behavioural cues. The quality of sedation training, nursing workload and regional economic disparity affected the sedation practice. The restricted visiting policy and lack of clearly defined nursing responsibilities around sedation may hinder effective sedation assessment and management. This study found that there was no paediatric‐validated tool popularized in paediatric intensive care units in China and explored influencing factors. We suggest that a validated tool, high‐quality training and hospital's policy, such as visiting regulation, should be promoted to improve the sedation practice.