Abstract: Objective To examine epidemic trend of class A and B infectious disease in Tibet Autonomous Region(Tibet) from 1976 to 2010 and to provide evidences for the prevention and treatment of infectious diseases in Tibet.Methods Data on class A and B infectious diseases in Tibet from January 1976 through December 2010 were collected;morbidity rate,mortality rate,and case fatality rate of all the national notifiable infectious diseases were calculated annually based on the population size.Results The total morbidity,mortality,and case fatality rate of infectious diseases among Tibetan people decreased from 2 572.20/100,000,10.49/100,000,and 0.41% in 1976 to 530.19/100,000,1.67/100,000,and 0.31% in 2010,respectively,all with a statistically significant decrease (P<0.05 for all);the top 5 class A and B infectious diseases with high morbidity were dysentery (909.01/100 000),measles (194.06/100 000),pertussis (92.49/100 000),tuberculosis (76.83/100 000),and viral hepatitis(60.81/100 000),accounting for 82.31% of all the class A and B infectious diseases reported;the top 5 infectious disease with high mortality rate were viral hepatitis (7.78/100 000),dysentery (3.32/100 000),measles (2.26/100 000),pertussis (0.89/100 000),and epidemic encephalitis (0.67/100 000),accounting for 95.86% of all class A and B infectious diseases reported;the top 5 infectious diseases with high case fatality rate were plague (56.32%),acquired immunodeficiency syndrome (AIDS)(27.27%),anthrax (13.92%),viral hepatitis (12.79%),and epidemic encephalitis B (10.84%).Conclusion Mortality,morbidity and case fatality of class A and B infectious disease were declining,but dysentery,measles,pertussis,tuberculosis,viral hepatitis,epidemic encephalitis B,plague,AIDS,and anthrax are the focal point of prevention and control of A and B infectious diseases in Tibet.