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Objective To establish a new standard for measurement islet autoantibodies by electrochemiluminescence (ECL) assay and to discuss its applications for type 1 diabetes mellitus (T1DM) prediction and diagnosis. Methods ECL assay was used to measure serum levels of glutamic acid decarboxylase antibody (GADA65), insulin autoantibody (IAA) and protein tyrosine phosphatase antibody (IA-2A) in 124 healthy volunteers, 180 T1DM patients, and 180 type 2 diabetes mellitus (T2DM) patients. Patients admitted in Sir Run Run Hospital, Nanjing Medical University from December 2016 to June 2018 with diagnosis of T1DM or T2DM were enrolled in the study. Healthy volunteers were recruited from students in Nanjing Medical University. The serum antibody level was represented as antibody index. The positive cut-off limit for each antibody was defined as 99% of the indicated antibody index from healthy volunteers. The chi-square test was used to analyze the positivity of GADA65, IAA, IA-2A of T1DM and T2DM patients detected by ECL method. Results The cut-off points for GADA65, IAA and IA-2A were 0.047, 0.009 and 0.0029 respectively by ECL methods. The intra-assay coefficients of variation (CV) for GADA65, IAA and IA-2A were 1.88% - 8.30%, 1.39% - 3.40%, 1.23% - 3.17% respectively, and the inter-assay CV were 3.9%-7.3%, 2.7%-9.8%, 2.2%-7.4% respectively. The repeatability of the result was 99.8%. The positivity of GADA65, IAA, IA-2A were 52% (94/180), 45% (81/180), 21% (39/180) respectively in T1DM patients and were 2.2% (4/180), 2.2% (4/180), 2.2% (4/180) respectively in T2DM patients. There were statistic significances in positivity between T1DM and T2DM for all three antibodies (χ²=113.57, 32.35, 91.31, all P<0.001). The positive ratio of GADA65 and IA-2A detected by ECL or radio-binding assay shows no difference. Conclusion The ECL assay has high sensitivity, specificity and repeatability and could be used for the prediction and diagnosis of T1DM. [ABSTRACT FROM AUTHOR]