The aim of this study is to Investigate of mechanism of supplementation effect with omega-3 on lipid profile and peroxidation , inflammatory markers, insulin resistance and liver function in patients with non-alcoholic fatty liver. this is a double blind clinical trial. for confounding variables controlling for sex and Body mass index by subject matching classifying will be done and randomely divided into 2 groups. 40 patients classified into omega-3 treatment group with 20 subjects and placebo group with 20 subjects. After selecting and grouping them under the supervision of a specialist, sampling and assay parameters will perform. patient>18 year with elevated Alanine aminotransfrase for up to 6 month before beginning of the study, lack of excessive alcohol ingestion, ultrasound examination demonstrating fatty liver, negative diagnostic tests for viral hepatitis, and absence of other causes of liver disease. Exclusion criteria included a history of alcohol intake,the use of drugs known to be associated with liver steatosis, undernutrition, chronic viral hepatitis, and chronic liver disease of other causes. Moreover, patients younger than 18 years as well as pregnantand breastfeeding women were excluded.