This study was designed as double-blind double-dummy randomized controlled multicenter clinical trial to evaluate the efficacy and safety of theophyiline-kelotifen sustained-releasing compound tablets in the treatment of asthma compared with theophylline sustained-releasing tablets. In the randomized groups, the study drugs were enveloped in double-blind double-dummy manner. The subjects with mild asthma took 3 pills (1 big pill and 2 small pills),q 12h for I week and those with moderate asthma for 6 weeks. The efficacy was investigated on nearly half of the subjects in each group after one-dose administration. The clinical efficacy of the tested group after 1-week duration was similar to that of the control group, and so as the results of lung function efficacy. After 6-week treatment, the clinical efficacy rate was 82.9% which was better than that of the control group; and the lung function efficacy rates were 90.8% and 82. 1 % respectively in the two groups. The investigation on one-dose administration suggested the study drugs had the characteristics of sustained releasing. The rate of adverse drug reactions of theophylline-ketotifen compound tablets was 7.7%.