Objective：The gonion and gnathion of human skull play an important role in forensic identification，dental surgery，cosmet－ic surgery and other fields. It is critical to locate them in cone bean（ＣＢ） CT mandible image for forensic identification and preopera－tive preparation. Methods：In this paper，an effective method was proposed to position gonion of mandible accurately and automatically. Firstly，265 CBCT mandible images were processed to extract the outer contour of lower jawbone by mathematics morphology method. Then quintic polynomial equations were carried out to gain fitted curves of mandible contours which were used to find the maximum curvature points. Lastly，distance correlation coefficient was computed to evaluate the accuracy of location of gonion objectively. Re－sults：Data showed that the distance between right and left gonion point to gnathion point had good correlation and the distance corre－lation coefficient was r=0.955. Conclusion：Finding the maximum curvature point with curve-fitting is an effect way to position the gonion in the CBCT mandible image.