INTRODUCTION: Malocclusion has a high prevalence and great harm. In Yunnan Province, China different in geographical environment, cultural practices, dietary habits, and uneven distribution of dental resources may lead to regional differences in malocclusion incidence and its effects on oral health-related quality of life and social psychology. METHODS: This study employed random sampling to recruit 367 adults (aged 18-35) from Kunming City and Gongshan County. Malocclusion was evaluated using Angle classification and the Dental Aesthetic Index (DAI). The modified WHO questionnaire, OHIP-14 scales, and PIDAQ scales were used to assess the impact of malocclusion on oral health-related quality of life and social psychology. RESULTS: (1) Class I malocclusion predominated in both regions, with Kunming showing significantly higher Class II prevalence (p < 0.05) while Gongshan had marginally more Class III cases. Within Gongshan's ethnic groups, although Class I remained most common, the Lisu subjects exhibited higher proportions of both Class II and Class III malocclusions. (2) In Kunming, DAI scores significantly correlated with paternal education level. (3) Kunming subjects affirmed biting or chewing difficulties had higher DAI scores than those denied, while the opposite was observed among the Nu ethnic subjects in Gongshan. (4) Kunming subjects' DAI scores showed a significant negative correlation with dental confidence in PIDAQ scale. However, in modified WHO questionnaire, Nu ethnic subjects who afraided smiling due to tooth appearance had significantly higher DAI scores than those who did not. CONCLUSION: (1) The prevalence of malocclusion varies in different regions. (2) There are certain differences in the types of malocclusion among different nationalities in the same area (Gongshan). (3) In two regions, the severity of malocclusion could affect the oral health-related quality of life and social psychology.