Abstract：Objective：To observe the clinical efficacy of Huayu Xiaoshuan Decoction combined with angiotensinconverting enzyme inhibitor （ACEI） in the treatment of elderly hypertension complicated by lacunar infarction，and to explore its effects on blood pressure circadian rhythm， cerebral blood perfusion， collateral circulation， and perivascular spaces. Methods： A total of 120 elderly patients with hypertension complicated by lacunar infarction admitted to Anyang Traditional Chinese Medicine Hospital from January 2022 to December 2023 were selected and randomly divided into the control group and the study group using the random number table method，with 60 cases in each group. During the study， one case dropped out from the control group and two cases from the study group. The control group received routine symptomatic treatment plus Benazepril Hydrochloride Tablets， while the study group received Huayu Xiaoshuan Decoction in addition to the treatment of the control group. The treatment course for both groups was three months. The clinical efficacy and the incidence of adverse reactions， as well as traditional Chinese medicine syndrome scores， blood pressure circadian rhythm [24-hour mean systolic/diastolic blood pressure （SBP/ DBP）， daytime mean SBP/DBP， nighttime mean SBP/DBP， nighttime SBP/DBP reduction rate， SBP/DBP load values]， cerebral blood perfusion parameters [mean flow velocity （Vm） and pulsatility index （PI） of the anterior cerebral artery （ACA） and middle cerebral artery （MCA）]， American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology （ASITN/SIR） collateral circulation grade， and perivascular space scores were compared between the two groups before and after treatment. Results： The total effective rate was 96.54% （56/58） in the study group and 83.04% （49/59） in the control group，with a statistically significant difference between the two groups （P＜0.05）. After treatment， the sub-item scores of traditional Chinese medicine syndrome including dizziness and blurred vision， chest pain， limb numbness， palpitations， shortness of breath， fatigue， spontaneous sweating，and the total traditional Chinese medicine syndrome scores decreased in both groups compared to before treatment （P＜0.05），and the above scores in the study group were lower than those in the control group （P＜ 0.05）. After treatment， there were no statistically significant differences in 24-hour mean SBP/DBP， daytime mean SBP/DBP， nighttime mean SBP/DBP， and SBP/DBP load values compared to before treatment in both groups （P＞ 0.05）；the nighttime SBP/DBP reduction rates increased in both groups compared to before treatment （P＜0.05），and the reduction rate in the study group was higher than that in the control group （P＜0.05）. After treatment，ACA Vm and MCA Vm levels increased in both groups compared to before treatment （P＜0.05），and the levels in the study group were higher than those in the control group （P＜0.05）；ACA PI and MCA PI values decreased in both groups compared to before treatment （P＜0.05），and the values in the study group were lower than those in the control group （P＜0.05）. After treatment，the ASITN/SIR collateral circulation grades improved in both groups compared to before treatment （P＜ 0.05），and the improvement in the study group was superior to that in the control group （P＜0.05）. After treatment， perivascular space scores decreased in both groups compared to before treatment （P＜0.05），and the score in the study group was lower than that in the control group （P＜0.05）. There was no statistically significant difference in the incidence of adverse reactions between the two groups （P＞0.05）. Conclusion：Huayu Xiaoshuan Decoction combined with ACEI in the treatment of elderly patients with hypertension complicated by lacunar infarction can alleviate various clinical symptoms， effectively regulate blood pressure circadian rhythm， reduce blood pressure variability， improve cerebral blood perfusion，promote collateral circulation，reduce perivascular spaces，and enhance clinical efficacy.