Objective It was designed to investigate the possibility of differentiating thyroid nodular malignacy, through observation on its changes of intra-vascularity and microvessel density. Methods Altogether 112 patients with 128 thyroid nodules, which were confirmed by operation and pathology, were retrospectively analyzed. Among these patients, there were 49 males with 51 nodules and 63 females with 77 nodules. Two dimentional features about the nodular size, aspect ratio, shape, boundary, inner echogenicity and microcalcifications were carefully observed and measured. Color Doppler flow imaging (CDFI) signals inside the nodular lesions were graded semi-quantitatively, and the distribution of CDFI signals were classified as graded types. Moreover, the value of microvessel density (MVD) was semi-quantitatively measured and calculated through microvessel endothelium labelled by immunocytochemical method with CD34. Results Of all these 128 nodules, there were 81 nodules proved to be patological malignacy, which the other 47 nodules being pathologically non-malignant. There were significant differences between malignant nodules and non-malignant nodules in low inner echogenicity, irregular shape, indistinct boundary, value of aspect ratio great than or equal to 1 and inner microcalcifications.it was showed by intranodular graded Doppler flow signals that about 78.12% of the nodules were hypervascularity, the other 21.88% were hypovascular. Among thoses thyroid nodules with hypervascularity, 64% were malignant and 36% were benign. Moreover, of those malignant nodules, approximately 52.3% showed polycentric or surrounding flow signals, while about 10.9% of them showed hypovascular inside the nodules. On the contrast, of those nonmalignant nodules, only 29.7% manifested as polycentric or surrounding flow signals, and 7.0% as hypovascular inside the nodules. It was also demonstrated that values of MVD inside the malignant nodules were significantly higher than that of the nonmalignant nodules. Conclusion The above results suggested that low echogenicity, indistinct boundary and intranodular microcalcifications may have better specificity and sensitivity. Increased polycentric or surrounding Doppler flow signals were important sonographic features, but should not be considered as key poit for differential diagnosis. There was obvious inconformity between intranodular MVD and intranodular Doppler flow gradings and types, which mechnisms should also be further investigated.