Objective: To investigate the clinical study of combination of inhaled corticosteroid (ICS)+β2 receptor agonist (LABA)+inhaled long-acting muscarinic antagonist (LAMA) in the treatment of patients with asthma-chronic obstructive pulmonary disease overlap syndrome (ACOS). Methods: Totally 66 ACOS patients in the People’ s Hospital of Ningdu County were selected from January 2023 to May 2024, and were divided into conventional group (33 cases, ICS combined with LABA) and study group (33 cases, LAMA on the basis of conventional group) according to the random coin tossing method. After 20 days of continuous treatment, the disease assessment [chronic obstructive pulmonary disease assessment test (CAT), asthma control test (ACT)], lung function indicators [maximum forced expiratory volume in the first second (FEV1), peak expiratory flow (PFE), FEV1/forced vital capacity (FVC) ratio], immune function indicators [CD3+T cell, CD4+T cell, CD4+T/CD8+T cell ratio] and adverse reactions were analyzed in the two groups. Results: After 20 days of treatment, the CAT score in the two groups of ACOS patients was lower while the ACT score was higher than that before treatment, and compared with conventional group, the CAT score in study group was lower while the ACT score was higher (P<0.05). Compared with the same group before treatment, the FEV1, FEV1/FVC and PFE in both groups were increased after 20 days of treatment, and the indicators in study group were higher than those in conventional group (P<0.05). The levels of CD3+T, CD4+T and CD4+T/CD8+T in the two groups after 20 days of treatment were higher than those before treatment, and the levels were higher in study group than those in conventional group (P<0.05). Comparison of total incidence rate of adverse reactions in ACOS patients revealed a small difference between study group and conventional group (P>0.05). Conclusion: The combination of ICS+LABA+LAMA in patients with ACOS can effectively improve the disease status, and significantly regulate the lung function and immune function, and it has good safety.