Abstract: To study the histopathological changes in digestive system spontaneous lesions of breeding macaca mulatta，the tongue, cheek pouch, esophagus, stomach, intestine, salivary glands, gall bladder and pancreas samples from the monkey of 2～20 years old were investigated by routine histological technique. The results showed that various spontaneous lesions including inflammatory cell infiltration, degenerations and necroses in mucosa,atrophy and proliferations in digestive glands, totaling 32 kinds in different degrees, were found in 92. 3% of the monkeys. The organ total detectable rate is higher in large intestine,check pouch and small intestine,and lower in esophagus and salivary gland. The degree and the frequency of lesions increased with age. It is suggested that spontaneous lesions should be monitored in safety estimation experiment of new medicine.