Abstract:For th e purpose of understanding the characterization and epidemiological significances of the Tibetan sheep plague,some clinical indices have been studied by conducing an experiment to observe how the Tibetan sheep was infected by Yersinia pestis.In the test.most of the infected sheep had the incubation period of 1to 2 days,or even more than 5 days in son1e cases. Mainly had the continued medium fever 1-2 degree centigrades abOve normal body temperature. The fever duration was 3-8days,or up to 14 days in certain sheep.The procrastination process was present 1n 68.36%of the tested sheep. Nearly 56.96.of the sheep could self convalesce.There were no specific symptoms or syndromes arising in the tested sheep,which was clinically similar to pasteurellosis.The results of serological testing PHA showed that the FI antibody titer raised in 4-8 days in the sheep that were infected via iv,S.C. ,mouth or insect vector,respectively,peaked in 10-20days(from 1:320 to 1 :81,920),and gradually descended after 60 days. The antibody disappeared until 200 days in some sheep.The bacteria of Y. pestis could be detected in various organs from the dead sheep in which the liver,spleen,lung and glands the high detection rate of bacteia. The chronic bacteria carrying duration could be up to 30 days only in a few sheep.