【Abstract】 Objective：To investigate the correlation between CEUS quantitative parameters and extrathyroidal extension (ETE) of thyroid papillary carcinoma (PTC). Materials and methods: A retrospective analysis in February 2013 to November 2019 in the affiliated Renmin Hospital,Jiangsu University,of papillary thyroid carcinoma (PTC), 112 cases of patients (157 nodules), preoperative CEUS in check, for PTC with ETE and without ETE group, internal echo,the size of the edge, blood flow signal, vertical ,horizontal diameter ratio, strengthen, uniformity, and enhance the strength of variables do chi-square test or the Mann - Whitney U test, then using Logistic regression analysis of risk factors for the screening of PTC ETE, further drawn half quantitative analysis parameters of the peak down time (time from peak to one half, TPH), increase the slope (wash in slope, WIS) and tumor size in the diagnosis of ROC curve, the maximum yoden index is the best boundary point, determine the quantitative parameters sensitivity, specificity of diagnosis of PTC ETE. Results: The qualitative characteristics (tumor size) of CEUS were significantly different between the PTC with ETE and without ETE group (P< 0.05). The difference of CEUS 'peak intensity (PI) between PTCwith ETE and without ETE group was statistically significant (P < 0.05). Multivariate Logistic regression analysis showed that tumor size, TPH, and WIS were independent risk factors for the ETE that diagnosed PTC (OR =3.688、0.892、9.758, P < 0.05). For the quantitative analysis parameters, the ETE value that diagnosed PTC with TPH value was the largest, and its area under the ROC curve was 0.805.The best cut-off value is 60.96 ,sensitivity and specificity were 88.3％、60.8％. Conclusion: The TPH and WIS of CEUS and tumor size were correlated with the ETE of PTC diagnosis.