This is a randomized, single-blinded, multi-center study clinical trial to determine both clinical and health outcomes of stratified warm strategy to prevent intraoperative hypothermia. Participants enrolled into this trial will be from elective major surgery population in PUMC Hospital, Beijing Hospital and Xuanwu Hospital. investigators plan to enroll approximately 800 participants. Hypothermia risk will be evaluated through PREDICTOR model in all participants. According to hypothermia risk level, these participants will be stratefied into high, moderate and low risk group. Participants in each group will be randomly categorize into warm group and control group. Active warm and fluid warm strategy, prewarm and fluid warm strategy and only prewarm strategy are used for high risk, moderate risk and low risk patients seperately. For controll group traditional passive warm was used.