This is a descriptive study that analyzes factors in personal relationships, such as self-esteem, parent-child relationships and friendships, to identify the factors that affect the formation of a mature personality in adolescence. The study conducted a self reported structured questionnaire of 152 high school students in Chungnam, Korea. They participated in research from August 14 to September 30, 2017. Results were performed analysis using descriptive statistics, t-test, ANOVA and Pearson’s correlation by SPSS program ver. 22.0. The analysis results are as follows: among the subjects studied, there are 56 male students (36.8%) and 96 female students (63.2%). The level of self esteem, friend-ship, parent-child relationship and personality showed very high (respectively 4.5±0.4, 3.2±0.33, 3.2±0.43 and 3.2±0.3). The relationship between influencing factors and personality fined out a significantly positive correlation. In conclusion, this study will be established the direction and provided basic data for formation of personality in adolescence. Moreover, it was required the development of adolescence personality education programs and it will be certainly needed to foster mature personality.