Background: Cardiovascular disease is the leading cause of mortality and morbidity worldwide, Chronic stable angina (CSA) is the main symptom of myocardial ischemia, causes increased risk of major cardiovascular events such as sudden cardiac death and myocardial infarction. Naoxintong (NXT) capsule is a classical traditional Chinese medication used to treat CSA, however, few evidence to support the wide utility of NXT capsule for the treatment of CSA. We design this study to evaluate the efficacy and safety of NXT capsule versus placebo in patients with CSA. Methods/design: This is a multicenter, randomized, double-blind, placebo-controlled clinical trial. A total of 260 eligible participants will be enrolled. The participants will be randomized assigned in an equal ratio to groups receiving either NXT or placebo for 12 weeks. After a 2-week run-in period, they will receive either NXT or placebo (3 pills, 3 times daily) for 12 weeks. The primary outcome is therapeutic efficacy. Secondary outcome measures include the quantitative score of TCM syndromes, severity grading of angina pectoris, the number of angina pectoris per week, nitroglycerin dosage, score of Seattle angina scale, serum homocysteine, and incidence of cardiovascular events. Safety outcomes and adverse events will be monitored throughout the trial. Discussion: We designed this study in accordance with principles and regulations issued by the China Food and Drug Administration (CFDA). The results will provide clinical evidence of the efficacy and safety of NXT Capsule in the treatment of CSA. Trial registration: Chinese Clinical Trial Registry ChiCTR2100044563. Registered on 24 March 2020. © 2021, The Author(s).