Abstract: Objective: To evaluate the beforetreatment and posttreatment changes in hard tissue of children in mixed dentition with class Ⅲ malocclusion treated with protraction face mask.Methods: 21 Chinese children（10 boys,11 girls） with class Ⅲ malocclusion were included.The mean age before treatment was 9 years 7 months（range 8 years 11 months to 11 years 3 months）.For each patient,a lateral cephalogram was taken before treatment（T1）,immediately posttreatment（T2）.（Results: A positive） overjet was obtained in all cases after 6 to 10 months of treatment.Immediately posttreatmeant,the maxilla moved anteriorly a mean of 1.92mm and SNA increased 2.53 degree.The maxillary insisors proclined 3.82 degree,whereas the mandibular incisors were uprighted,the mandible rotated in a downward and backword direction,the mandibular plane angle increased,improving facial profile.Conclusion: Face-mask can be used effectively in class Ⅲ malocclusions in mixed dentition,improving class Ⅲ facial profile.