Objective：To research the gene mutation of 3-ketothiolase（3KT）（T2） in non-diabetic ketoacidosis，to provide references for diagnosis of 3-ketothiolase deficiency（3KTD），to reveal the role of T2 in isoleucine metabolism and to explore potential mecha－nisms of 3KTD by gene mutations. Methods：DNA was extracted from peripheral blood of the patients，his family members and healthy children. The entire coding regions of T2 gene with flanking intronic regions were amplified by PCR and the amplified products were directly sequenced and mutation sites were detected. Results：A127V missense mutation in exon 5 was identified in proband and no mutation was observed in other tests. Some single nucleotide polymorphisms（SNPs） of T2 gene were detected. Conclusion：A127V in exon 5 of T2 gene may be a potential pathogenesis of 3KTD.