The invention relates to an antigen used for the early diagnosis of haemonchus contortus infection, and application thereof. The invention authenticates an antigen used for parasite infection, and theamino acid sequence of the antigen is disclosed in SEQ ID NO.1. The antigen can be used for carrying out specific recognition on an antibody in the serum of a host infected with the haemonchus contortus for 14 days, a definite diagnosis is made before 4-6 days of ovum ovulation, and the pollution of the ovum for the environment and a pasture can be avoided so as to perform an important meaning for the prevention and control of the haemonchus contortus disease. By use of the antigen disclosed by the invention, the antigen is used for establishing an indirect ELISA (Enzyme Linked ImmunosorbentAssay) detection method, and therefore, the antigen has the advantages of being high in sensitivity, good in specificity, simple in operation, high in diagnosis speed, economic, convenient and the like during large-scale detection, and has a good application prospect in the diagnosis, the prevention and the curing of the haemonchus contortus disease of ruminants, including cows, goats, deer, camels and the like.