Objective: To identify the prevalence of sleep problems in children with autism spectrum disorder (ASD) and to explore the association with the main melatonin metabolite, 6-sulfatoxymelatonin (6-SM). Method: This was a prospective case-control study. Children with ASD were recruited from Child Development and Behavioral Research Center (CDBRC) of the Harbin Medical University and Harbin Special Education School from October 2015 to April 2017 (ASD group) . Healthy controls were selected from five kindergartens and one primary school in Harbin by the stratified cluster random sampling (control group) . The Children's Sleep Habits Questionnaire (CSHQ) was used to investigate the sleep problems of the two groups. The patients were matched in a 1∶1 ratio for the age and sex, and the urine samples of case-control pairs were collected in the morning. The level of 6-SM was measured by the enzyme linked immunosorbent assay (ELISA). The student's t test was used for comparison between the ASD group and control group, and the Pearson correlation analysis was used to determine the correlation difference. Result: A total of 212 ASD children (mean (±SD) age was (6.0±2.7) years, and 181 patients (85.4%) were male), and a total of 334 healthy children(mean (±SD) age was (5.9±2.6) years, and 272 patients (81.4%) were male) were recruited. Among them, 101 matched case-control pairs completed the collection of urine samples. According to the statistical analysis, the scores of total CSHQ, bedtime resistance, sleep onset delay, sleep duration, night waking, parasomnia, sleep disordered breathing and daytime sleepiness in children with ASD were significantly higher than those in the control group (48.2±6.2 vs. 46.6±5.4, 11.4±2.5 vs. 10.7±2.8, 1.7±0.8 vs. 1.5±0.7, 4.1±1.4 vs. 3.7±1.1, 4.2±1.5 vs. 3.8±1.1, 8.5±1.5 vs. 8.3±1.4, 3.7±1.0 vs. 3.4±0.8, 11.7±2.5 vs. 12.4±2.7, t=3.16, 3.00, 3.23, 2.76, 3.19, 1.99, 3.45,-2.72, P=0.002, 0.003, 0.001, 0.006, 0.002, 0.048, 0.001, 0.007), the level of 6-SM was significantly lower in children with ASD than that of healthy controls ((1.24±0.50) vs. (1.68±0.63)μg/h, t=-5.50, P<0.01), and the total CSHQ score was negatively correlated with the level of 6-SM (r=-0.50, P<0.01). Conclusion: The children with ASD were at high risk for sleep problems, and the melatonin metabolite of ASD group was abnormal compared with that of the control group. Moreover, there was a negative correlation between the severity of sleep problems and the level of 6-SM in ASD children. The results of our study indicate that the abnormal melatonin metabolism may be one of the causes of sleep problems in children with ASD.