Objective: To study the influence of age on the ratio of various types of immune cells and the distribution of pathogenic bacteria in patients with pulmonary tuberculosis complicated with lower respiratory tract infection. Methods: A retrospective analysis was performed on 113 patients with tuberculosis complicated with lower respiratory tract infection (tuberculosis group) admitted to Wuxi Fifth People’s Hospital from January 2016 to May 2020, and 45 healthy subjects who underwent physical examination during the same period were selected as the control group. According to the age of the tuberculosis group, the patients were divided into the elderly group (age ≥60 years), the middle-aged group (age 40–59 years), and the youth and middle-age group (age 18–39 years). Flow cytometry was used to determine the ratio of CD3⁺, CD4⁺, CD8⁺, NK cells and B cells in different groups. The sputum specimens of the elderly group, the young and middle-aged group were collected for common culture, and the distribution of infection pathogens were compared. Results: Compared with the control group, the levels of CD3⁺, CD4⁺, NK cells, B cells in the tuberculosis group were significantly reduced, and the level of CD8+ was significantly increased. The differences between the groups were statistically significant (all P<0.05). The levels of CD3⁺, CD4⁺, NK cells and B cells in the elderly group were significantly lower than those in the youth and middle-age group; the level of CD8⁺ was significantly higher than those in the youth and middle-age group, and the differences between the groups were statistically significant (all P<0.05). Except for Escherichia coli and Staphylococcus aureus, the distribution rate of other pathogens in the elderly group was higher than that in the young and middle-aged groups, and the differences between the groups were statistically significant (all P<0.05). Conclusion: Elderly patients with pulmonary tuberculosis and lower respiratory tract infection have lower immune function than young and middle-aged patients, and the infection rate of pathogens is higher than that of young and middle-aged people. We should pay more attention to their immune function and pathogen infection.