Abstract： Objective To investigate the role of uncoupling protein (UCP)3 gene polymorphism in pathogenesis of obesity with or without type 2 diabetes in Northern Han population. Methods Subjects were 100 obese patients (BMI 34.3±9.6 kg/m2), 60 with T2DM and 40 without T2DM, and 40 healthy subjects as control. G304A polymorphism,C427T mutation and exon 6 splice junction polymorphism of UCP-3 gene were separately determined with polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP). Results Neither G304A polymorphism nor exon 6 splice junction polymorphism was found in 140 subjects, however, one patient with obesity and T2DM was identified as a C427T heterozygote. Conclusion The mutation of G304A of UCP-3 gene and GGT→GAT exon 6 splice junction as well as C427T mutation may not be involved in the pathogenesis of obesity and type 2 diabetes in Northern Han population in china.