Abstract: Nonalcoholic fatty liver disease（NAFLD）  is a spectrum of disorders  ranging from simple steatosis (nonalcoholic fatty liver，NAFL)  to nonalcoholic steatohepatitis (NASH)， cirrhosis and cancer. As  a spectrum of severity， NAFLD is not a single metabolic disorder. This article begins with the definition of NAFLD， describes the assessment and quantification of hepatic steatosis， the epidemiology and pathogenesis of NAFLD， and the endocrine and metabolic disorders associated with NAFLD. Diet and intestinal flora can promote the occurrence and development of NAFLD. Based on epidemiology， dietary habits and obesity and other related factors， diabetes and NAFLD are closely related.Furthermore， the two have formed a vicious circle. To some extent， diet and drug intervention can alleviate the incidence and development of NAFLD and diabetes mellitus.

Key words: fatty liver, nonalcoholic；hepatitis, nonalcoholic steatohepatitis； diabetes mellitus, diet； intestinal flora