Objective:To investigate the application value of shear wave elastography (SWE) in the evaluation of T re-staging after neoadjuvant chemoradiotherapy (nCRT) for locally advanced rectal cancer.Methods:Clinical, endorectal ultrasound (ERUS) and SWE data of 271 patients with locally advanced rectal cancer who underwent nCRT and total mesorectal excision in Fujian Medical University Union Hospital from October 2021 to March 2023 were prospectively collected. The independent predictors for low T staging were analyzed and screened, and the Logistic regression model was constructed. An independent test set was used to validate the prediction performance of the models and compare them with the diagnostic results of sonographers.Results:Binary multivariate Logistic regression analysis showed that Emean of the mesentery around the lesion, thickness, and enlarged lymph nodes around the rectum were the independent predictors for low T staging, and the odds ratios were 1.089, 1.214, 0.183, respectively. The Logistic regression model A established by Emean, thickness and enlarged lymph nodes around the lesion and the Logistic regression model B established by Emean around the lesion had high diagnostic efficiencies (area under the ROC curve were 0.931, 0.918, respectively, the accuracy were 0.888 and 0.887, respectively). There was no significant difference in diagnostic accuracy between the two models ( P=1.000), and both models were significantly higher than that of sonographers (all P<0.001). Conclusions:SWE can effectively predict whether the tumor is of low T staging after nCRT in locally advanced rectal cancer, and can be used as an important supplement to ERUS in evaluating the T re-staging of rectal cancer after nCRT.