Abstract： Objective To investigate CT features on increased cerebral vascular density and its pathological mechanism in patients with cyanotic congenital heart disease(CCHD).Methods Preoperative brain CT scan and clinical data in 82 patients suffering from CCHD were analyzed. According to the increased levels of vascular density,patients were divided into 4 groups:normal,mild,moderate and severe.Relationships between the increased levels of vascular density and Hb,RBC,HCT,as well as the degree of cyanosis,were studied.AVONA was carried out to test blood CT value of cerebral sinuses,Hb,RBC and HCT in different groups. Descriptive analysis and linear regression were adopted to study the correlation between blood CT value and Hb concentration.The relationship of increased vascular density to degrees of cyanosis was analysed by Spearman.Results Among 82 patients,12 patients ( 14.6％ ) were found in the group of normal vascular density and 70 patients ( 85.4％ ) in the increased vascular density group.Among 70 patients with increased vascular density,22 patients (26.8％ ) with (55.4 ± 2.6) HU,(169 ±6)g/L of Hb,(5.8 ±0.3) × 1012/L of RBC and 0.51 ±0.03 of HCT,29 patients (35.4％) with (61.3 ± 2.9) HU,(209 ± 15 ) g/L,(7.1 ± 0.4) × 1012/L,0.66 ± 0.06 and 19 patients ( 23.2％ ) with ( 68.8 ± 4.2) HU,( 242 ± 23 ) g/L,( 8.3 ± 0.9 ) × 1012/L,0.78 ± 0.08 were observed in the mild,moderate and severe group,respectively.There were significant differences in distribution of blood CT value ( HU),Hb,RBC and HCT in different groups ( F =163.263,134.703,120.974,136.541 ;P ＜ 0.01 ).Blood CT value was positively correlated with Hb concentration ( r =0.98,P ＜ 0.01 ). Vascular density was also positively correlated with the degree of cyanosis ( r =0.86,P ＜ 0.01 ). Conclusions Cerebral vascular density of patients suffering from CCHD presented different levels of increases based on CT scan results due to rise of RBC stimulated by anoxia.The increased level of vascular density was positively correlated with blood Hb concentration,and also associated with RBC accunulation caused by abnormal blood circulation.Moreover,it was positively correlated with the degree of cyanosis.