Abstract: In order to provide scientific grounds for the prevention and treatment of penicillic acid poisoning on the poultry and the mechanism of penicillic acid toxicosis,the toxicity of penicillic acid has been investigated in broiler chickens.By the artificial contamination,we observed the pathological manifestation and measured the changes of blood biochemical value,the residue of penicillic acid in tissue and organs of the broiler chickens within 60 days.The results showed that:1)major pathological changes was fatty and vacuolar degeneration of hepatocytes,cloudy swelling of renal epithelial cells and myocardial cells;2)the contents of MCV and MCHC in poisoned groups were less than that in control group,whereas the activities of SGPT,LDH and AKP in the formers were higher than those in the latter;3)as for the distribution of penicillic acid,the amount was the highest in liver,and the residue in kidney outweighed that in heart.It was understandable that there was a relation between the residue of penicillic acid and the degree of lesion.The target organ of penicillic acid poisoning was liver.