Objective: To investigate the correlation of shear-wave elastography (SWE) parameters with protein expression and molecular subtype in breast invasive ductal carcinoma (IDC). Methods: A total of 184 invasive ductal cancers in 182 women underwent SWE before surgery or biopsy. Two elastographic images from two orthogonal planes were obtained for each lesion. SWE elastic quantitative parameters, including the maximum stiffness (E_max), mean stiffness (E_mean), ratio of stiffness of the mass to stiffness of the surrounding fatty tissue (E_ratio) were measured with region of interest (ROI) =2 mm. The pathologic results and protein molecules (ER, PR, HER2, Ki-67, p53) expression were anayled and detected, respectively. Based on the protein molecules expression, the tumors were divided into four subtypes: Luminal A, Luminal B, HER2-enriched and Basal-like. We used Student’ t-test or one-way ANOVA and multiple linear regression to evaluate the correlation of between elastic quantitative parameters with protein molecular expression and molecular subtypes. Results: At univariate analysis, lesion size, histologic grade and Ki-67 expression were significantly associated with the maximum stiffness square root and mean stiffness square root (all P<0.01). Only the difference in logarithm of E_ratio between tumors of different sizes was statistically significant (P<0.001). There was no significant relationship between molecular subtypes and quantitative elasticity values. By multivariate analysis, only lesion size was independent statistically associated with quantitative elasticity values. Conclusion: The bigger the lesion, the higher the elasticity values, the harder the lesion. We were unable to demonstrate a correlation between protein molecule expression and molecular subtypes and tumor hardness.