The study investigated the burden of smear-positive pulmonary TB and its infectivity using DALY(disability-adjusted life year) as an indicator. Methods An assumed cohort of 2 000 cases was set up based on the age-specific incidence of 794 newly registered smear-positive cases in Beijing in 1994. Prognostic trees and model diagrams of infectivity under natural history and DOTS(directly observed treatment, short-course) strategy were established according to the epidemiological evidence. Results The results showed that 29.6%of DALYs would be neglected if the burden caused by the infectivity was not considered.Conclusion DOTS strategy may reduce 97.3% of the number of potential cases infected,92.9% of DALYs related to TB-patients themselves. and 99.9% of DALYs caused by TBs infectivity as well.