Abstract: Objective To investigate the condyle-fossa relationship alterations in patients with skeletal class Ⅲ malocclusion following maxillary protraction therapy in mixed dentition by spiral CT scanning technique. Methods Fifteen patents with skeletal class Ⅲ malocclusion in mixed dentition, ranging in age from six years seven months old to ten years three months old, were treated with maxillary protraction. The patients underwent conventional 16 slice computed tomography scanning from PHILIPS company，and then 3D reconstruction was done to the skulls. Mid-sagittal images of the temporomandibular joints（TMJ）were evaluated for the possible changes in condyle-fossa relationship before and after treatment. Measurement items included the anterior joint space, the superior joint space, the posterior joint space, glenoid fossa depth and angulation of posterior wall of articular tubercle. Paired t test was applied to evaluate the differences. Results No statistically significant differences were found except superior joint space and posterior joint space before and after treatment. Conclusion The superior and poserior joint space decreased and condyle moves posterosuperiorly in patients with skeletal class Ⅲ malocclusion following maxillary protraction therapy in mixed dentition.