Objective To obtain the acceptable range for posed smile characteristic index,in order to supply diagnostic and therapeutic basis for orthodontic treatment.Methods The 200 subjects included in the study consisted of 100 experienced orthodontists and 100 laypersons.Both two frontal posed smile photographs of man and woman were changed by several smile characteristic indexes,including the amount of incisor exposure,amount of gingival display,smile arc,buccal corridor fill,horizontal inclination of maxillary occlusal plate and distance from lower lip to maxillary incisor.All the subjects were desired to evaluate each images according to their own aesthetic standard.Results Each acceptable range for the amount of incisor exposure,amount of gingival display,smile arc,buccal corridor fill,horizontal inclination of maxillary occlusal plate and distance from lower lip to maxillary incisor,was 75 ％-100 ％ (male and female),0-2 mm (male) and 0-3 mm (female) ; 50 ％-100 ％(male and female) ; 0 ％-15 ％ (male) and 0 ％-20 ％ (female) ; 0-6° (male and female) ; 0 mm (male and female)(P＜0.05),respectively.And there was perception difference between the orthodontists and the laypersons on smile evaluation (P＜0.05).Conclusions Posed smile analysis should be an im portant aspect of orthodontic diagnosis and treatment planning.Orthodontists should not disturb con sonant smiles but create them with proper bracket positioning.