Objective To investigate the expression of serum miR-140-3p in children with autism spectrum disorder (ASD) and its correlation with interleukin-4 ( IL-4),interleukin-8 (IL-8) and interleu-kin-17A (IL-17A),and provide evidence for the diagnosis and treatment of ASD. Methods Totally 172 ca-ses of ASD children admitted to Anning Hospital of Hainan Province from January 2015 to June 2018 were selected as case group,80 cases of healthy subjects as control group. ASD children were divided into mild-moderate group (n=116) and severe group (n=56) by ASD Behavior Rating Scale and Child Autism Rating Scale. Real-time fluorescence quantitative polymerase chain reaction ( RT-PCR) and enzyme-linked immu-nosorbent assay ( ELISA) were used to detect the changes of serum levels of miR-140-3p,IL-4,IL-8 and IL-17A in each group. ROC curve was used to analyze the diagnostic value of miR-140-3p,IL-4,IL-8 and IL-17A for ASD. Pearson correlation was used to analyze the correlation between serum miR-140-3p and IL-4,IL-8 and IL-17A in children with ASD. Results The serum levels of miR-140-3p ( 0. 86 ± 0. 17 vs 0. 15±0. 03),IL-4(48. 65±13. 82)pg/ml vs (31. 42±7. 50)pg/ml),IL-8((7. 14±2. 05) pg/ml vs (2. 30± 0. 74)pg/ml) and IL-17A((112. 35±51. 64)pg/ml vs (58. 20±26. 40)pg/ml) in the case group were sig-nificantly higher than those in the control group ( P<0. 05). Serum levels of miR-140-3p( 1. 08 ± 0. 24 vs 0. 71±0. 12),IL-4((53. 28±16. 30)pg/ml vs (43. 70±13. 52)pg/ml),IL-8((9. 42±2. 85)pg/ml vs (5. 63 ±1. 48)pg/ml) and IL-17A((138. 40±65. 72)pg/ml vs (96. 74±40. 83) pg/ml) in severe group were sig-nificantly higher than those in mild-moderate group(P<0. 05). The AUC (95%CI) of serum miR-140-3p for ASD diagnosis was 0. 827 (0. 773-0. 886),which were significantly higher than that of IL-4 (0. 719 (0. 651-0. 764)pg/ml),IL-8 (0. 683 (0. 625-0. 743)pg/ml) and IL-17A(0. 745 (0. 683-0. 817)pg/ml). The best cut-off value was 0. 75,and the sensitivity and specificity were 84. 8% and 78. 2%,respectively. The best cut-off value of serum miR-140-3p for diagnosing ASD was 0. 75, and its sensitivity and specificity were 84. 8% and 78. 2%,respectively. The correlation analysis showed that serum miR-140-3p was positively cor-related with IL-4,IL-8 and IL-17A in children with ASD (r=0. 681,r=0. 624,r=0. 775,all P<0. 01). Con-clusion Serum levels of miR-140-3p was significantly higher in ASD children, correlated with levels of IL-4,IL-8 and IL-17A,and miR-140-3p was a potential biomarkers for ASD diagnosis.