Objective To evaluate the value of color flow angio(CFA)in judging the status of thyroid function by analyzing the ultrasonographic features and quantitatively measuring the blood flow signals in patients with thyroid diffuse lesions.Methods Totally 100 patients with thyroid diffuse lesions diagnosed by ultrasonography between Oct.2016 and Jun.2017 were divided into three groups:hyperthyroidism group(n=30),hypothyroidism group(n=34)and euthyroid group(n=36).Moreover,30 cases of healthy volunteers were chosen as control group.The blood flow index including vascularity index(VI)value and Vascularity value of region of interest from all cases was measured through CFA imaging technique.The differences of VI and Vascularity from above 4 groups were compared using one-way analysis of variance.Comparison among groups was carried out by SNK-q test.The subjects' work curves(ROC curves)were plotted and analyzed using clinical diagnosis as gold standard.At the same time,the correlation between VI and thyroid function in hyperthyroid group and hypothyroidism group was analyzed through Pearson correlation coefficient.Results The levels of VI and Vascularity in hyperthyroid group,hypothyroid group,euthyroid group and control group were decreased gradually with significant differences between every two groups.VI : control vs hyperthyroid,hypothyroid and euthyroid group: q=13.67,7.00 and 3.93,all P＜0.01.Euthyroid vs hyperthyroidism and hypothyroid group: q=10.35,P＜0.01 and q=3.27,P＜0.05.Hyperthyroidism vs hypothyroid group: q=7.09,P＜0.01.Vascularity: control vs hyperthyroid,hypothyroid and euthyroid group: q=15.23,10.16 and 6.58,all P＜0.01.Euthyroid vs hyperthyroidism and hypothyroid group: q=9.33 and 3.83,both P＜0.01.Hyperthyroidism vs hypothyroid group: q=5.55,P＜0.01.The area under the curve of hyperthyroidism group and hypothyroidism group was 0.733,with 9.526%as the diagnostic cutoff point.The sensitivity and specificity were 70.0%and 76.5%respectively.The area under the curve of the abnormal group and normal group was 0.768,with 7.404%as the diagnostic cutoff point.The sensitivity and specificity were 62.5%and 88.9%,respectively.The VI value of hyperthyroidism group was positively correlated with FT3 and FT4(r=0.584,0.499,both P＜0.05),and negatively correlated with TSH(r=-0.447,P＜0.05).The VI value of hypothyroidism group was negatively correlated with FT4(r=-0.342,P＜0.05),and had no significant correlation with FT3 and TSH(r=0.121,-0.007,P＞0.05).Conclusion CFA imaging technology can quantitatively measure the blood flow signals of thyroid parenchyma and evaluate the thyroid function in patients with thyroid diffuse lesions.