ABSTRACT Objective To investigate the diagnostic value of TI-RADS 3 or 4 in Small thyroid nodules by conventionaland contrast-enhanced ultrasound（CEUS）.Methods For 88 cases of TI-RADS 3 or 4 in Small thyroid nodules retrospective analysis of the characteristics of ultrasound（nodule size, aspect ratio (A/T), boundary, echo, microcalcification, blood flow signal, lymph nodes around the neck） and CEUS(nodular enhancement time, enhancement uniformity, enhancement mode, enhancement intensity, variation of nodular size after enhancement, boundary of nodular enhancement after enhancement, and presence of ring enhancement)，and T test (homogeneity of variance), χ2 test, Logistic regression analysis, ROC curve analysis and consistency test statistical analysis were performed for these indicators.Results Logistic regression analysis of conventional US showed that microcalcification，and suspicious lymph glands are risk factors for malignant thyroid micronodules，while logistic regression analysis of CEUS showed that slow enhancement time and absence of rim-like enhancement are risk factors for malignant thyroid micronodules.Logistic regression analysis of conventional US combined with CEUS demonstrated that microcalcification，suspicious lymph gland，slow enhancement time，and absence with rim-like enhancement are risk factors.The ROC curve for conventional US，CEUS，and conventional US combined with CEUS were 90.0%，90.7%，99.0%，respectively.The correlation between the diagnosis of thyroid micronodules and pathological diagnosis was higher（Kappa=0.813，P=0.000）.Conclusion Our results show that conventional US combined with CEUS had superior diagnostic performance for TI-RADS 3 and 4 thyroid micronodules compared with conventional US and CEUS alone.