The invention discloses a tooth root extraction method based on an oral CBCT image, and the method comprises the following steps of S100, carrying out the optical scanning, obtaining a three-dimensional tooth jaw and dentition model, and building a projection image and a CBCT file sequence; S200, analyzing the CBCT file sequence through a Marching,Cube and a region growing algorithm; S300, based on the CBCT file sequence, distinguishing the upper tooth jaw and the lower tooth jaw, wherein the distinguishing process comprises the steps that the key frames of the occlusal plane and the sagittalplane are positioned through VTK, and a restrictive region growing algorithm is executed; S400, optimizing the segmentation effect of upper and lower tooth jaws, and manually cutting the tooth jaw model; and S500, removing the noise image of the cut tooth jaw model, and smoothing the noise image. According to the present invention, the surgical risk is reduced, and the surgical success rate is increased.