To observe the effects of Xiaoxinbi formula on left ventricular diastolic function and heart rate variability (HRV) in patients with hypertrophic cardiomyopathy (HCM).Methods:Seventy-two patients diagnosed with HCM were selected and randomized into two groups.The control group (35 patients) was given routine western medication, including β-blockers.The treatment group (37 patients) was given routine western medication plus Xiaoxinbi formula, twice daily.Both of the treatment lasted for 90 days.Chinese medicine symptoms, echocardiography changes, as well as HRV parameters were observed and analyzed before and after the treatment.Results:The symptoms of fatigue, breath shortness, palpitation, chest distress, and loss of appetite syndrome in the treatment group were significantly improved compared to the control group (P<0.05).Besides, the parameters of echocardiography were significantly improved compared to those of the control group after the treatment (P<0.05).Meanwhile, the NYHA levels were also significantly improved compared with those of the control group after the treatment (P<0.05).Additionally, the parameters of HRV were also significantly improved compared with those in the control group after the treatment (P<0.05).Conclusion:Xiaoxinbi formula has obvious clinical effects in improving the TCM symptoms of fatigue, breath shortness, palpitation, chest distress, and loss of appetite.It can improve left ventricular function, and the possible mechanisms may be related to HRV improvement and sympathetic activity inhibition.