A computer-aided positioning and navigation system for dental implant includes a computer system having built therein a dental implant planning software and providing a 3D digital human tissues model to create an implant navigation information, a positioning assistive device including a body providing a positioning portion and a guide portion and a connection member carrying an optical positioning device, one or multiple optical capture devices, and a display device electrically connected to the computer system. The computer system controls the optical capture device to capture images and drives the display device to display a part of the content of the 3D digital human tissues model and the implant navigation information.