The embodiment of the invention discloses an automatic planning method and device for the optimal position of an in-bone implant. The safety of selected screw channels is ensured, and the optimal screw channel can be automatically generated. The method includes the steps that a geometric model of a target skeleton after fracture reduction is obtained, and with a pre-appointed screw inlet point anda pre-appointed screw outlet point on the target skeleton being seed points, a surface point set of the geometric model around the screw inlet point and a surface point set of the geometric model around the screw outlet point are obtained; for the first point set and the second point set, one point is selected from the first point set and one point is selected from the second point set each time,the two selected points are utilized for generating a cylinder, the cylinders are determined to be safe screw channels if it is found that the cylinders are located in the geometric model through judgment, all combinations of the first point set and the second point set are traversed, and all the safe screw channels are determined; the optimal screw channel is selected form the safe screw channels.