Objectives : This research was investigated to evaluate the psychological characteristics and changes of psychological state among dental orthodontic patients. Methods : This cross-sectional questionnaire research was conducted with 230 dental orthodontic patients in Busan from December 23, 2009 to March 6, 2010. The psychological analysis of dental orthodontic treatment patients was performed with Symptom checklist-90-revision(SCL-90-R) considering 5 general characteristics and 2 treatment period related characteristics. Estimated psychological results were changed T-score. Data analysis was performed with descriptive analysis, t-test and ANOVA using SAS(ver 9.1) program. Results : The levels of T-score of SCL-90-R were $43.88{pm}7.50$ in hostility(HOS), $43.38{pm}4.64$ in phobic anxiety(PHOB), $43.20{pm}6.24$ in somatization(SOM), $42.13{pm}6.71$ in paranoid ideation(PAR), $41.39{pm}8.16$ in interpersonal sensitive(I-S), $41.01{pm}7.90$ in obsessive-compulsive(O-C), $40.96{pm}5.37$ in psychoticism(PSY), $40.96{pm}5.19$ in anxiety(ANX) and $39.81{pm}6.80$ in depression(DEP), respectively. The T-score of phobic anxiety in before treatment group was higher than that of treatment groups. The T-score of interpersonal sensitive and paranoid ideation in over 36 months treatment period group were higher than that of other treatment period groups. Conclusions : Phobic anxiety(PHOB), interpersonal sensitive(I-S) and paranoid ideation(PAR) were affected in pre-treatment and long-term treatment dental orthodontic patients. Psychological management methods considering treatment period are needed to improve mental health of dental orthodontic patients.