Objective To investigate the correlation of slow wave power δ/α ratio(DAR)and δ power value on quantitative electroencephalography(QEEG)with cognitive dysfunction in patients with cerebral small vessel disease(CSVD).Methods A total of 80 patients with CSVD who were treated in Department of Neurology,Affiliated Hospital of Chifeng University,from January 2022 to October 2023 were enrolled and evaluated using Montreal Cognitive Assess-ment(MoCA)scale,and QEEG was performed to calculate DAR and δ power value.Related statistical analyses were per-formed.Results There were 40 CSVD patients in the cognitive dysfunction group,with average education years of(8.50±2.00)and a mean age of(62.38±6.32)years,among whom there were 8 female patients(20%)and 32 male patients(80%).There were 40 CSVD patients in the normal cognitive function in group,with average education years of(8.00±4.00)and a mean age of(63.60±7.14)years,among whom there were 10 female patients(25%)and 30 male patients(75%).There were no significant differences in years of education,age,and sex between the cognitive dysfunction group and the normal cognitive function group(P>0.05),while there was a significant difference in MoCA score between the cog-nitive dysfunction group and the normal cognitive function group[8-24(14±9)points and 26-28(26.00±1.00)points,Z=-7.822,P<0.05].The cognitive dysfunction group had significantly higher DAR and δ wave power values than the nor-mal cognitive function group(P<0.05).Cognitive dysfunction in CSVD was negatively correlated with slow wave power DAR and δ power value on QEEG(P<0.05).Conclusion DAR and δ power values on QEEG are correlated with cogni-tive dysfunction in patients with CSVD,suggesting that DAR and δ power values can be used as indicators for identifying cognitive dysfunction in patients with CSVD.