Abstract: Objective To probe etiopathogenesis of secondary infection caused by diarrhea in one Macaca speciose thibetanas. Methods The pathological observation on an 8 year-old Macaca speciose thibetanas with historically recurring diarrhea were carried out. Results Macaca speciose thibetanas was in the the dehydrant condition as showed in the clinical symptom. Also serious pathologyical change was observed in the lung and intestine. Histopathologically, granular degeneration and vacuolar degenera-tion were observed in the liver and kidneys. Congestion and hyperemia were observed in the blood vessel of many tissues and organization, and the inervallum of vessel wall was swollen. Pancreas，bladder and brain were normal. Conclusion The characters of diarrhea in Macaca speciose thibetanas are complex etiological factors and seasonal occurrence. The treatments on diarrhea of such animal are suggested to mainly depend on TCM and modern treatments to be adjuvant.

Key words: Macaca speciose thibetanas, Diarrhea, Secondary infection, Pathology