Abstract: Objective To explore MDOY1 gene mutations in pedigrees of early-onset familial type 2 diabetes. Methods We collected 100 early-onset type 2 diabetes pedigrees in Beijing, in which the probands were diagnosed with type 2 diabetes before the age of 40 years with at least one first-degree relative having such a diagnosis before the age of 45 years. PCR was employed to amplify all the exons and exon/intron splice sites of MDOY1 gene and the PCR products were sequenced to identify the DNA variants. Results Two DNA variants in the noncoding region including IVS1C +44A>T and IVS2 -5C>T were identified, and 3 mutations in the coding region we identified M49V, T130I, and S462S were found in these pedigrees. Conclusion Currently no sufficient evidence has been obtained to identify the variation in or near MDOY1 genes as the major cause of early-onset type 2 diabetic in Chinese population.