Abstract: Objective To the compare serum immunoglobulin E (IgE), C-reactive protein (CRP) and interleukin-6 (IL-6) in patients with asthma, chronic obstructive pulmonary disease and asthma-chronic obstructive pulmonary disease and its clinical significance. Methods A total of 65 patients with asthma-chronic obstructive pulmonary disease in Fangshan Hospital, Beijing University of Chinese Medicine, from March 2018 to January 2020 were selected as a research group, while another 65 patients with asthma and 65 patients with chronic obstructive pulmonary disease were selected as a control A group and a control B group, respectively. They were compared for general information, serum IgE, CRP, and IL-6 levels, lung function indicators forced expiratory volume in the first second as a percentage of predicted value (FEV1%), and forced vital capacity (FVC), and blood gas analysis indexes arterial partial pressure of oxygen (PaO₂), and arterial partial pressure of carbon dioxide (PaCO₂). The relationship between serum IgE, CRP, IL-6 and pulmonary function indexes and blood gas analysis indexes was evaluated. The application of serum IgE, CRP, and IL-6 in the diagnosis of asthma-chronic obstructive pulmonary disease was explored. The prognosis of the research group after treatment for three months was calculated.Their general information before treatment and serum IgE, CRP and IL-6 one levels and three weeks after treatment were compared. Results The research group presented increases in the levels of serum IgE, CRP, IL-6 and PaCO₂, as well as decreases in FEV1%, FVC, and PaO₂, compared with the control A group and the control B group (P＜0.05). The levels of serum IgE, CRP, and IL-6 were negatively correlated with FEV1% (r=-0.674, -0.489, and -0.716), FVC (r=-0.689, -0.715, and -0.691) and PaO₂ (r=-0.884, -0.789, and -0.821), but positively correlated with PaCO₂ (r=0.664, 0.514, and 0.646) (P＜0.05). The area under the curve (AUC) of the combination of serum IgE, CRP, and IL-6 for the diagnosis of asthma-chronic obstructive pulmonary disease was 0.876, which was higher than that of each index alone (0.817, 0.846, and 0.737). The optimal sensitivity and specificity of the combined diagnosis was 75.38% and 89.23%, respectively. The levels of serum IgE, CRP and IL-6 in the patients of the research group with good prognosis were lower than those with poor prognosis after three-week treatment (P<0.05). Conclusions The levels of serum IgE, CRP and IL-6 in patients with asthma-chronic obstructive pulmonary disease significantly increased. Early determination of each index can reflect the patient's lung function and blood oxygen status to a certain extent, assist clinical diagnosis due to its relationship with patient prognosis, and provide important evidence for the clinical diagnosis and treatment of asthma-chronic obstructive pulmonary disease.