ObjectiveTo observe the clinical efficacy and mechanism of Tongnao Yizhi Formula （通脑益智方， TYF） in treating vascular cognitive impairment no dementia （VCIND） with spleen and kidney depletion， phlegm and stasis obstructing collaterals syndrome. MethodsNinety-two VCIND patients with spleen and kidney depletion， phlegm and stasis obstructing collaterals syndrome were randomly divided into control group （42 cases） and treatment group （52 cases）. Both groups received routine basic treatment. The control group was given donapezil hydrochloride capsules orally， 5 mg each time， once at night， while the treatment group was given TYF orally， 1 dose per day. Both groups were treated continuously for 3 months. The scores of Mini-Mental State Examination （MMSE）， Vascular Dementia Assessment Scale-Cognitive Subscale （VaDAS-Cog）， Activity of Daily Living Scale （ADL）， and TCM syndrome scores （the primary symptoms such as sluggish thinking， forgetfulness， temperament changes， and language confusion， and secondary symptoms such as weakness of waist and knees， dizziness and headache， occasional tinnitus， fatigue， heaviness of limbs， insomnia and irritability， poor appetite and abdominal distension， numbness of face） were observed before and after treatment in both groups. The changes in gut microflora diversity and flora abundance structure as well as fecal short-chain fatty acids （SCFAs） levels including acetic acid， propionic acid， butyric acid， isobutyric acid， isovaleric acid， valeric acid， and caproic acid were compared between groups. The feces of 20 healthy subjects in the same period were included as reference. Safety was evaluated during the study. ResultsAfter treatment， both groups exhibited significant increases in MMSE scores and decreases in VaDAS-cog scores （P＜0.05 or P＜0.01）， and ADL scores in the treatment group significantly increased （P＜0.05）. Scores of symptoms including sluggish thinking， forgetfulness， temperament change， language confusion， heaviness of limbs， insomnia， irritability， poor appetite， abdominal distension， and facial numbness as well as the total score significantly decreased in both groups after treatment （P＜0.05 or P＜0.01）. When compared between groups， the treatment group showed substantial reductions in scores of weakness of waist and knees， tinnitus， fatigue， heaviness of limbs， insomnia， irritability， loss of appetite and abdominal distension （P＜0.05 or P＜0.01）. The gut microflora diversity analysis showed that the Shannon index of the treatment group significantly increased after treatment （P＜0.05）.PCoA analysis and ANOSIM test indicated significant differences between groups， suggesting changes in microflora species （P＜0.01）. After treatment， the relative abundance of Bacteroidetes and Fusobacteria in the treatment group increased， while the relative abundance of Actinobacteria， Verrucomicrobia and Cyanobacteria decreased （P＜0.05）； the relative abundance of Faecalibacterium prausnitzii， Bifidobacterium， Lactobacillus， and Ruminococcus increased significantly （P＜0.05）. Compared to the the gut microflora species diversity of the healthy people， it is indicated that the gut microflora structure in the treatment group was close to that of the healthy people， while there was no such trend in the control group. In the treatment group， acetic acid， propionic acid， and butyric acid in the treatment group were all higher after treatment （P＜0.05 or P＜0.01）. ConclusionsTYF can improve the cognitive ability and quality of life of VCIND patients with spleen and kidney depletion， phlegm and stasis obstructing collaterals syndrome， and this improvement may be related to regulating intestinal microecology.