Objective: To investigate the specifity of amyloid precursor protein(APP), brain derived neurotrophic factor (BDNF)and gamma aminobutyric acid(GABA) in peripheral blood in children with autism spectrum disorder, so as to explore the biomarkers for early screening of ASD and its relationship with the severity of ASD. Methods: A total of 41 children diagnosed with autism from January to December 2019 were enrolled in the ASD group. Meanwhile, 41 healthy children with normal growth and development who were examined in the same period were selected as control group. And the sera total sAPP, sAPP α, sAPP β, BDNF and GABA of all participants were tested by sensitive enzyme linked immunosorbent assay method, and were compared between the two groups. Results: The serum sAPP level in ASD group(2 132.98±333.28 ng/mL) was higher than control group(1 734.76 ±357.97 ng/mL),the serum sAPP α level(335.11±33.87 pg/mL) was higher than control group(274.84±32.12 pg/mL) and the serum GABA level(4.17±0.95 μmol/L)was lower than control group(6.35±0.84 μmol/L). GABA level (4.17±0.95 μmol/L) was lower than that of control group (6.35±0.84 μmol/L), the differences were statistically significant ( t =3.92, 4.25, -7.27, P < 0.05 ). In addition, the serum GABA level in children with severe ASD (3.48±0.77 μmol/L)was lower than children with mild to moderate (4.94±0.98 μmol/L).The difference was significant ( t =-3.31, P <0.05). ROC curve showed that total sAPP( AUC = 0.77 ,95% CI =0.66-0.87), sAPP α( AUC =0.77,95%CI=0.67-0.87), and GABA ( AUC =0.95,95% CI =0.90-0.93)had diagnostic efficacy for ASD( P <0.05), among which the AUC of GABA was the largest (0.95)and its sensitivity(85.65%) and specificity(80.76%) were the highest. The results of binary Logistic regression showed that the abnormal expression of sAPPα ( OR =1.04,95% CI = 1.00- 1.07) and GABA( OR =0.02,95% CI =0.00-0.32) were associated with risk for ASD( P <0.05). Conclusion Considering the specific change of total sAPP, sAPPα andGABA in peripheral blood in ASD children, total sAPP, sAPP α and GABA can be considered as promising biomarkers in the early diagnosis of ASD, among which GABA has the highest sensitivity and specificity.