Fasciolosis cause economic losses in cattle that breed in Iraq and the world. About 4% of bovine liver’s samples included in the current study exhibited classical pathological lesions of fasciolosis. Samples of cattle livers infected with fasciolosis were taken for histopathology. Eighteen grading criteria with four scoring level have been chosen to grading the microscopic lesions caused by Fasciola hepatica into a mild infection (grade I), moderate infection (grade II) and severe infection (grade III). The type of hepatic degeneration or necrosis, cloudy cell swelling, coagulative necrosis, infiltration of inflammatory cells, with patterns of infiltration, also type of infiltrated cells, fibrosis between hepatic cells or in portal area, affection to hepatic cords arrangement, hepatic sinusoids, extensions of hemorrhage, pigment deposition, hyperplasia of bile duct, thickness of hepatic capsule and presence of liver fluke were the main grading levels. In grade, I the microscopic lesions were characterized by simple or mild in their nature with very good reversible prognosis, while grade II characterized by moderate severity of the lesions with a good reversible prognosis, while grade III characterized by hostile severity with bad irreversible prognosis as a result of architecture changes in liver histology. In conclusion, we believed that this grading system could be used as a guide when examining histopathological liver's samples infected with F. hepatica to identify the stage of infection and proposed an accurate prognosis.