The objective of the study was to investigate the morphological changes of skeletal class III malocclusion in mixed dentition with light force protraction combined activities. Randomly selected 30 eases of orthodontics in Shanxi Medical University orthodontics patients (ages: 6-10 years) of the lateral cephalograms. Using the oral maxillary casting type of pre-traction device, according to the condition of maxillary dentition to select the corresponding activities of the movable expansion appliance, each side of the force of about 1 50-200 g, requiring patients to wear 10-12 hours a day, the appliance should be removed after reaching normal occlusion. The correlation cephalometric profile of the cranial lateral radiographs before and after orthodontic treatment was measured. All patients with skeletal class III malocclusion were improved, concave type became direct type, measurements SNA, ANB, A-Ptm, MP-SN, AN S-Me/N-Me increased, maxillary advancement and reconstruction are more obvious; mandible rotates clockwise; the increase of lip inclination of anterior teeth compensatory changes, lower anterior tooth inclination changes smaller; upper lip forward, nasolabial angle decreased, improved appearance significantly. Light force protraction combined activities can make the mixed dentition of skeletal class III malocclusion in patients with significant improvement in profile appearance.