Objective To understand the occurrence of hypothermia and changes of temperatures in ICU patients during the first 24 hours of continuous renal replacement therapy (CRRT) and to provide reference for improving warming techniques. Methods A retrospective study was conducted. Demographic data of the ICU patients on CRRT in 2019, CRRT flow parameters, and the lowest body temperatures within 0-, 4-, 8- and 12-24 h after CRRT initiation were collected through the electronic medical record system, intensive care information system and CRRT nursing record sheet.Results A total of 784 CRRTs performed in 213 patients were analyzed. Hypothermia (core temperature<36℃) was noted in 84 patients (39.4%) and their APACHE Ⅱ score, SOFA score and the mortality rate were significantly higher compared with those without hypothermia (P<0.01 for all). Hypothermia was developed in 122 CRRTs (15.6%) and the temperature decreased significantly within 4 hours after CRRT initiation (P<0.05), whereas it wasn′t enhanced within the next 20 hours. The rate of mechanical ventilation was higher, whereas the body temperature before CRRT was lower during the CRRT treatments which developed hypothermia (P<0.01 for both). Conclusion The prevalence of hypothermia within 24 hours after CRRT initiation is relatively high in ICU patients, and the rewarming effect is not satisfactory, indicating the conventional heat preservation/rewarming techniques need to be further optimized.