Abstract: [Abstract] Objective To investigate the clinical value of polar coordinate measuring method through analyzing effect of adults skeletal cross-bite malocclution. Methods 18 adults skeletal cross-bite patients (aged 18-23, average 20.8, 9 men, 9 women) were chosen. In these cases,four premolars were extracted. Lateral cephalograms were taken at central occlusion position for all of them befor and after treatment. The system of polar coordinates was established with the Bolton Point (Bo) as the pole, and the Bo-N Line as the polar axis. The polar angles and the polar radiuses of soft and hard tissue marking points of maxilla-mandibular facial region were measured respectively. The measured data were processed by SPSS 17.0 with pair t test. Results All cases were treated successfully. Bo-L1 was decreased significantly by 6.54mm in average (P<0.01), Bo-LL was decreased by 3.51mm and Bo-U1 was increased 2.17mm respectively in average (P<0.05). Conclusions Polar coordinates can be used to accurately describe as a whole the craniofacial features for the skeletal cross-bite patients. Soft and hard tissue profiles were improved significantly after treatment . [Key Words] Extraction therapy ; Skeletal cross-bite;Polar coordinates