ObjectiveTo evaluate the effect and safety of Jiuxin Pill （救心丸） on exercise tolerance and quality of life in patients with stable angina pectoris （SAP）. MethodsA randomised， double-blind， placebo-controlled， multicentre study design was used to enroll 170 patients of SAP from nine centres， which were divided into 85 patients each in the trial group and control group with 1∶1 ratio. Both groups maintained the original western medicine treatment plan， and added Jiuxin Pill or placebo respectively， 2 pills （0.05 g） each time twicely for 28 days. The main outcomes were total exercise time （TED） in the exercise treadmill test and Seattle Angina Questionnaire （SAQ） scores including physical limitation （PL）， angina stability （AS）， angina frequency （AF）， treatment satisfaction （TS）， and disease perception （DP）. The secondary outcomes were exercise treadmill test indicators including heart rate recovery in 1 min （HRR1）， metabolic equivalents （METs）， maximum magnitude of ST-segment depression， and the Borg rating of perceived exertion scale， the average number of angina attacks per week， withdrawal and reduction rate of nitroglycerin， traditional Chinese medicine syndrome scores， incidence of major adverse cardiovascular events. Safety indicators were evaluated and the occurrence of adverse events during the trial was recorded. Data was collected before treatment， day 28±2 in treatment period， and follow-up at day 56 which is 28±2 days after treatment period finished. ResultsEighty-four and eighty-five patients respectively from trial group and control group were included to the full analysis set （FAS） and safety analysis set （SS）. Compared with the group before treatment and with the control group after treatment， the trial group had higher TED， HRR1， and METs， and lower maximum magnitude of ST-segment depression and Borg rating of perceived exertion scores after treatment （P＜0.01）. Compared with the group before treatment and with the control group after treatment and at follow-up， the total SAQ score and scores of AS， AF， TS and DP of the trial group after treatment and at follow-up elevated， while the average number of angina attacks per week and traditional Chinese medicine syndrome scores reduced （P＜0.01）. There was no statistically significant difference in the withdrawal and reduction rate of nitroglycerin between groups （P＞0.05）. Major adverse cardiovascular events occurred in 1 case （1/84， 1.19%） in the trial group and 1 case （1/85， 1.18%） in the control group， and the difference between groups was not statistically significant （P＞0.05）. A total of 3 cases of adverse events occurred in the trial group （3/84， 3.57%）， and a total of 6 cases of adverse events occurred in the control group （6/85， 7.06%）， and there was no statistically significant difference in the incidence of adverse events between groups （P＞0.05）. ConclusionIn the treatment of SAP， Jiuxin Pill combined with conventional western medicine can further enhance exercise tolerance， improve quality of life， and demonstrate great safety.