Objective  To explore the cortisol secretion levels and their related factors of children with autism spectrum disorder(ASD). Methods Fifty boys aged 6-12 years, with 30 in ASD group and 20 in typical development(TD) group, were included. The screen for child anxiety related emotional disorders-revised(SCARED-R), social responsiveness scale(SRS), and repetitive behavior scale-revised(RBS-R) were used to evaluate their anxiety, social ability and restricted and repetitive behaviors(RRBs) of ASD. Cortisol levels were measured via saliva at three time points(waking, 30 min after waking, and evening) across 2 d. Sleep patterns were evaluated by 14-day sleep diary. Multiple linear regression, with cortisols as dependent variables and their potential related factors as independent variables, was conducted to evaluate relative factors of cortisols of ASD. Results   Evening cortisol in ASD group（-0.13±0.50） nmoL/L was significantly lower than TD（0.34±0.34） nmoL/L. The sleep pattern significantly differed in two groups, with the characteristics of shorter 24-hour sleep duration and lower sleep efficiency in ASD group. The results of multiple linear regression showed that the evening cortisol level was positively associated with its sleep onset latency and negatively related to its RRBs. Conclusion   Evening cortisols are significantly different between ASD group and TD group. The cortisol level in ASD is associated with its sleep onset latency and RRBs.