Polycystic ovary syndrome is a metabolic disease(PCOS).Most patients have insulin resistance(IR) in PCOS.Insulin resistance is the pathophysiological basis of PCOS.Its mechanisms including obesity and PCOS itself.Patients have insulin resistance in any body weight.PCOS involving IR in insulin regulation of glucose metabolism in multiple organs and links.Ovary have IR too.Lifestyle changes,weight control and the use of insulin sensitizer in patients with polycystic ovary syndrome are the important therapeutic measures of IR.