Abstract: Background　Insulin resistance is a key factor of type 2 diabetes incidence. Vitamin K2 can improve insulin sensitivity but its related mechanisms have not been well established.Objective　To investigate the effects of vitamin K2 on insulin resistance of mice fed on a high fat diet and related mechanisms.Methods　Aged mice were divided into normal diet group (a standard diet and olive oil oral gavage), HFD (high fat diet, with olive oil oral gavage), and HFD-VK (high fat diet, with 120 mg/kg wt/wt vitamin K2 dissolved in equivalent olive oil oral gavage). Body weight was recorded every week. Fasting blood glucose and insulin were detected to evaluate HOMA-IR, intraperitoneal glucose tolerance tests (IPGTT) and intraperitoneal insulin tolerance test (IPITT) were used to examine the glucose disposal ability, HE staining was used to examine morphology of liver and white adipose tissue, Western blotting was used to investigate the protein levels of p-AMPK in liver and white adipose tissue.Results　 Compared with the HFD group, vitamin K2 administration significantly reduced body weight, decreased glucose and insulin in blood and thus exhibited an improvement in HOMA-IR; it increased glucose tolerance and insulin sensitivity and so improved glucose disposal ability (P＜0.05); and it could also improve morphology and activate AMPK in the liver and white adipose tissue (P ＜0.05).Conclusion　Vitamin K2 attenuates insulin resistance of mice fed on a high fat diet, which is related in activating AMPK in the liver and adipose tissue.