Objective To assess the reliability of sagittal position relation between maxilla and mandible with APDI. Methods Used the lateral cephalometric radiographs of orthodontics ago as materials and selected the 72 X-Ray films with Angle Ⅱ,Ⅲ malocclusion. Traced and measured the angles of FH-PP, FH-Npog, AB-Npog and APDI. Results ①In Angel Ⅱ Malocclusion, AB-Npog angle showed statistical difference on sex (P<0.01)。②In girl′s Angle Ⅱ malocclusion, there was correlation between APDI and AB-Npog angle (γ=0.591)....