Abstract: Objective To study the characteristics of arterial blood gas and electrolytes in patients with severe pulmonary tuberculosis with respiratory failure. Method In 50 patients with severe pulmonary tuberculosis, the arterial blood gas and electrolytes were measured after the onset of respiratory failure to define the types of respiratory failure and acid-base imbalance. Results Severe pulmonary tuberculosis with respiratory failure was characterized by development of hypoxia, and the degree of hypercapnia may vary; more extensive tuberculous involvement or longer disease course suggest greater chance of type Ⅱrespiratory failure. Increment of the anion gap occurred irrespective of the pH value. Conclusion Analysis of arterial blood gas and electrolytes may help monitor the progression of severe pulmonary tuberculosis and provides valuable information for implementing treatment and making prognostic decisions.