Objective To evaluate the efficacy of eucalyptol-limonene-pinene enteric capsule on stable chronic obstructive pulmonary disease (COPD) in the elderly. Methods A total of 120 patients with stable COPD were randomized into ELP group (n=63) with conventional treatment combined ELP and control group (n=57) with conventional treatment without ELP. Primary outcome was the number of exacerbations per year, and secondly outcomes were lung function parameters and St. George's Respiratory Questionnaire (SGRQ). Results After 1 year of treatment, numbers of exacerbations per patient per year were lower in ELP group than in control group (0.70 times/y vs. 1.21 times/y, Z=-3.887, P=0.000). The proportion of exacerbation-free patients were 25.4% (16/63) in ELP group and 5.3% (3/57) in control group (χ2=9.103, P=0.003). The differences in the forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and FEV1/ FVC ratio (FEV1%) between 5 different time points measurements were statistically significant in both groups (ELP group: F=15.429, 36.389, 33.278, respectively, all P=0.000; control group: F=54.238, 94.213 and 83.774, respectively, all P=0.000). Difference in FEV1/FVC ratio between 5 different time point was statistically significant in control group(F=2.766, P=0.043), but not in ELP group(F=0.861, P=0.451). After treatment, SGRQ score was decreased in both group, and difference in symptom score was statistically significant between the two groups (t=2.109, P=0.037). The adverse reactions were found in 3 cases in ELP group, and in 2 cases in control group with no statistically significant difference between the two groups 〔3 (4.8%) vs. 2 (3.5%), χ2=0.013, P=0.732〕. Conclusions Long-term oral administration of eucalyptol-limonene-pinene enteric capsule can significantly decrease exacerbation frequency, improve quality of life, delay the deterioration in lung function, and have good safety in elderly patients with stable COPD. Key words: Pulmonary disease, chronic obstructive; Respiratory function tests