The invention belongs to the field of fodder, and specially relates to a fodder acidulant, which is characterized by comprising the following raw materials in part by weight: 20-40 parts of lactic acid, 10-20 parts of citric acid, 10-20 parts of malic acid, 10-20 parts of tartrate, and 150-180 parts of bamboo vinegar liquid. The invention also provides an application method of the fodder acidulant, and the method specially is that the acidulant is added in an amount of 2-10 Kg per ton of fodder. The invention utilizes bamboo vinegar liquid combined with organic acid and inorganic acid to produce fodder composite acidulant which can reduce the acid-binding capacity of the fodder, substitute or partly substitute antibiotics. In addition, the composite fodder acidulant can perform opsonization for feeding pig intestines and inhibit the growth of pathogenic bacteria, has effective effect in solving problems of intestinal diseases and diarrhoea in pigs production, can promote health conditions of pigs, and improve production performance of pigs.