The invention belongs to the field of animal experimental models, and relates to a method for establishing a fish fatty liver experimental model. The method comprises the following steps of: 1) injecting physiological saline solution of thioacetamide into grass carp at one time in an intraperitoneal injection mode and culturing after injection is finished, wherein 1ml of physiological saline solution of thioacetamide comprises 100 to 200mg of thioacetamide; and 2) feeding a compound feed with the total grease content of 4 to 6 percent in the culturing process and culturing for two to six weeks. The thioacetamide is injected into the grass carp, so that hepatic and pancreatic tissues and cells of the grass carp are damaged, and the lipid metabolism and energy metabolism of the grass carp are interfered; meanwhile, the compound feed with appropriate grease content is fed, so that the experimental grass carp with fatty liver disease can be quickly obtained.