Abstract: Objective:The influence of music on the sleep cycle and brain electrical activity of preterm infants is still inconclusive. This article aims to observe the changes in the quiet sleep cycle(QSC) and EEG characteristics of preterm infants after music intervention. Methods: This study was a single-center randomized controlled trial. Preterm infants admitted to the Neonatal Department of Children's Hospital of Fudan University at 32 weeks ≤ gestational age <36 weeks were divided into a musical intervention group (intervention group) and a control group in the ratio of 1∶1 using a randomized numerical table. The intervention group was given Brahms lullabies at an average volume of 40-50 dB, played once every 24 h for 6 h. The intervention period was 1 week. The control group was given no musical intervention, and the nursing measures were the same as the intervention group. EEG monitoring was carried out for 6 h within 48 h after completion of the intervention in rhe two groups. The primary observation was the characteristics of the quiet sleep cycle, including mean QSC time, total QSC time, QSC frequency, QSC interruption frequency, and mean QSC interval. The secondary observation was the comfort score (COMFORTneo scale) and the amplitude integrated EEG outcome score (Burdjalov's method). Results: A total of 112 subjects completed enrollment from June 1, 2018 to June 30, 2019, with 56 in the intervention and 56 in the control group. The differences in baseline data between the two groups were not statistically significant. In terms of QSC characteristics, the mean QSC duration in the intervention group increased by 0.17 h (P=0.015), the total time of QSC occurrence during EEG monitoring increased by 0.52 h (P=0.033), and the number of QSC interruptions was three times fewer than that in the control group (P=0.003). For comfort score, the total scale score in the intervention group was 1.9 points higher (P=0.031) and the alertness score was 0.8 points higher (P=0.042) than those in the control group. For aEEG score, the sleep-wake cycle score was 0.7 points higher (P=0.043), the spectral bandwidth score was 07 points higher (P=0.019), and the overall score was 1.4 points higher (P=0.047) in the intervention group than those in the control group. Mean QSC time, total QSC time, total comfort score, and total aEEG score all increased with gestational age. There were positive correlations between gestational age and mean QSC time, total QSC time, comfort scores, and aEEG scores. Conclusion: Music intervention can affect the quiet sleep cycle and EEG activity of preterm infants, including increasing the time of single QSC, total QSC time, reducing the number of QSC interruptions, and actively improving the comfort score and EEG characteristics of preterm infants.