Purpose Accurate Tumor delineation during the surgery is a big challenge for surgeons. For instance, in transoral robotic surgery (TORS) for tongue base tumor resection, the preoperative images cannot accurately reflect the tumor area in the tongue, because of the soft tissue deformation during the surgery. Furthermore, due to the camera’s small field of view and the loss of cross-modality landmarks in the tongue base, it is difficult to register the preoperative image to the intraoperative stereo camera with deformable registration. We propose an intraoperative ultrasonography (IOUS)-based augmented reality (AR) framework which is able to accurately delimit the tumor boundaries and provide them to the surgeon’s view. Instead of some works requiring manual registration [1], additional fiducial markers [2], or intraoperative imaging modalities using ionizing radiation [2, 3], our solution uses safe and cheap US imaging and does not need additional fiducial markers disturbing the TORS workflow.