The aim of this randomized controlled clinical trial study was to evaluate the effect of Rosvastatin on steatosis and fibrosis in patients with non-alcoholic fatty liver disease. From patients who were referred to gastrointestinal clinic of Tohid hospital, Sanandaj, Iran total of 40 patients with non-alcoholic fatty liver disease were selected. Main inclusion criteria included: Non diabetic patients, normal FBS, BS2hpp, Hb1AC, age 20 years and older, approved non fatty liver diagnosed by fibroscan, LFT (AST and ALT), rejection of other causes of fatty liver disease such as hepatitis B and C. Main exclusion criteria included: patients who have other liver diseases, contraindication for Rosvastatin, not taking hypoglycemic drugs such as metformin. Patients randomly divided into intervention and control groups. Patients and researchers were blinded and were not aware of grouping. In intervention group patients received 10 mg Rosvastatin daily plus standard treatment for fatty liver disease. In control group patients received placebo daily plus standard treatment for fatty liver disease. Before intervention and six months after the intervention AST and ALT were controlled and also, liver steatosis and liver fibrosis re-measured by fibroscan.