Objective To investigate the effects of metformin on serum visfatin and the level of visfatin mRNA in visceral adipose tissue of type 2 diabetic rats.Methods Forty Wistar rats were randomly assigned into normal diet group (NC) and diabetic group.The rats in the diabetic group were fed with high glucose and high fat diet, and then injected with streptozotocin (STZ).The diabetic rats were divided into diabetic control (DC), metformin (MET), and insulin-treatment (INS) groups.Eight weeks later, body weight (BW) , visceral adipose tissue weight, and biochemical indicators were assessed.Homeostasis model assessment of insulin resistance (HOMA-IR) and Lee index were calculated.The serum visfatin levels were detected by enzyme-linked immunoassay (EIA), and the visfatin mRNA levels of visceral adipose tissues were detected by real time polymerase chain reaction (PCR).Results Compared to group DC, the visfatin levels of serum and visceral adipose tissue mRNA were lower in INS group, but did not have significant difference (P ＞ 0.05);the visfatin levels of serum and visceral adipose tissue mRNA in MET group were significantly lower (P ＜ 0.01).Conclusions Metformin can reduce the visfatin levels of serum and visceral adipose tissue mRNA, and improve the insulin resistance in type 2 diabetic rats.