Abstract： Objective To study a serum adiponectin level and a relationship between serum adiponectin and insulin resistance in metabolic syndrome (MS) patients without diabetes and to investigate its influence of rosiglitazone(RGZ). Methods Besides control group(n=30),92 MS patients without diabetes were divided randomly into A group(n=40,routine treatment ) and B group(n=52,plus RGZ). The serum adiponectin was measured by enzyme linked immunosorbent assay,HOMA-IR,and insulin sensitivity index(ISI) were calculated. Results The serum adiponectin was significantly lower in metabolic syndrome group than in normal control group［（1.15±0.81)mg/L vs (4.81±1.20 )mg/L, P<0.01］.The serum adiponectin level was negatively correlated with HOMA-IR（P<0.01）, and positively correlated with ISI（P<0.01）. There was a significant increase in serum adiponectin ［(2.52 ±1.37) mg/L vs （0.89±0.73)mg/L，P<0.01］ and ISI（-4.61±0.45 vs -4.61±0.45，P<0.01）, a significant decrease in HOMA-IR（0.99±0.35 vs 1.50±0.45，P<0.01）in B group versus A group. Conclusions The serum adiponectin in MS cases without diabetes is significantly decreased，negatively correlated with HOMA-IR. There is a significant increase in serum adiponectin and ISI, a significant decrease in HOMA-IR after RGZ treatment in MS cases without diabetes.