Abstract： Objective To compare the prevalences of the metabolic syndrome (MS) in type 2 ~diabetic (T2DM) patients using three definitions proposed by WHO,1999, NCEP-ATPⅢ,2001 and the Chinese Diabetes Society (CDS), 2003 respectively. Methods We screened 251 T2DM patients with less than one-year duration of diabetes and without the histories of coronary heart disease and stroke. The homeostasis model assessment was used to evaluate insulin resistance (HOMA-IR). The three definitions for dignosis of MS were compared in T2DM. HOMA-IR and the prevalences of ultrasonic macrovascular abnormalities were compared between the patients with and without MS. Results (1)The prevalences of the MS by the WHO, the CDS and the ATPⅢ criterium were 61.4%, 61.8% and 48.2%(P<0.01) respectively. The prevalence using the ATPⅢ criterium was lower than that using the other two criterium (P<0.01).(2)99.6% of the participants were similarly classified by the WHO and the CDS criterium.(3)The prevalences of central obesity by the criterium of WHO, CDS and ATPⅢ were 59.3%, 59.8% and 13.5%(P<0.01) respectively.(4)Using the ATPⅢ criterium, the levels of HOMA-IR, FIns and 2 hIns between the participants with and without MS were 5.2(3.4～8.3) vs 4.3(2.8～6.8) (P<0.05), 16.0(12.0～23.5) vs 14.0(10.0～20.0) mU/L(P<0.01), 48.0(33.0～77.0) vs 40.0(25.5～57.0) mU/L(P<0.01) respectively. Conclusions (1)The prevalences of MS using the three criterium were significantly different in the participants. The prevalence using the ATPⅢ criterium was lower than that by the other two criterium. The WHO and CDS criterium may be mutually applied in T2DM in Chinese. (2)It is more stringent in diagnosing central obesity using the ATPⅢ criterium. Close relationships between HOMA-IR and MS may be found using the ATPⅢ criterium in T2DM.