ABSTRACT Objective To investigate the value of transrectal biplane ultrasound (TRUS) for restaging and efficacy prediction of locally advanced rectal cancer (LARC) after neoadjuvant chemoradiotherapy (nCRT). Methods The clinicopathological data of 106 patients with LARC who received nCRT in our hospital were retrospectively analyzed and divided into the good response group (pTRG 0, 1, n=58) and the poor response group (pTRG 2, 3, n=48); the complete pathologic response group（pCR group, n=42）and non-response group（non-pCR group, n=64）.All patients underwent TRUS before and after nCRT , recording tumor length, thickenss, flow resistance index , elastography score, micro-flow grade, ultrasound T stage and TRG stage after nCRT . Comparing the consistency of uT stage and uTRG with pT stage and pTRG . The differences of ultrasound parameters between pCR and non-pCR group were compared. ROC curve was drawn to evaluate the value of TRUS parameters for pCR after nCRT in LARC. Results The concordance rate between uT and pT stage was 65.1% (Kappa = 0.517, P <0.05), and T3 had the highest accuracy of 78.8%. The concordance rate between uTRG and pTRG was 89.6% (Kappa = 0.789, P <0.05). There were significant differences in tumor length, thickenss, RI value, SE score, MFI grade both the pCR group and the non-pCR group after chemotherapy（all P <0.05）.The intra group comparison showed that tumor length, thickness and RI value of pCR group were less than those of npCR group while the length, thickness and RI value reduction rate of pCR group were higher than those of npCR group after chemotherapy, the difference were statistically significant（all P <0.05）. ROC curve showed that the cut-off values of length, thickness, and RI reduction rate to evaluate pCR after nCRT were 67.75%, 71.75%, 36.88%, with corresponding AUC areas of 0.884, 0.836, and 0.857, sensitivity of 84.4%, 92.2%, 93.8%, and specificities of 83.3%, 76.2%, and 66.7%, respectively. Conclusion TRUS shows good agreement with pTRG grade, and has great value in the assessment of pCR of locally advanced rectal cancer after neoadjuvant chemotherapy.