The period in primary school is important for children’s personality development. Peer plays an important role in personality formation and its development for children. We explored the effect of peer acceptance and friendship quality on personality development of primary school students in individual and class levels, by involving the peer factor as a circumstance variable, centralizing the peer acceptance and friendship quality in the within-class group respectively and aggregating individual peer acceptance and friendship quality as two class-level variables. We examined how peer acceptance and friendship quality influenced the personality development in primary school students on both individual and class levels. Our research breaks the limitation of ignoring the influence of class level social and psychological context effect in previous studies. We selected 700 participants as mutual friends with class for the unit, which were from 23 classes and 6 grades (1-6), using best friend nomination method. The data was collected by adopting peer nomination method and handing out the primary school students’ friendship quality questionnaire and the teacher-assessment primary school students’ personality development questionnaire. According to the lower-level mediation model (1-1-1), we respectively regarded the five dimensions of personality (intelligence, extraversion, pro-sociality, conscientiousness and emotional stability) as dependent variables in Hierarchical Linear Modeling (HLM), and examined the multilevel mediation effect of friendship quality on the relationship of peer acceptance and each dimension of personality by the multilevel mediation effect test procedures. The result indicates that:for example intelligence, the average level of peer acceptance in class has no a direct effect on intelligence(t=-0.090,p>0.05). Controlling the effects of class level, peer acceptance significantly predicting effects on intelligence in the path c(t=5.010,p<0.001).Peer acceptance have significance predicting effects on friendship quality in the path a(t=2.438,p<0.05), friendship quality and peer acceptance have significance predicting effects on intelligence in the path b and c'[b(t=3.308,p<0.05)and c'(t=5.065,p<0.001)] . Individual level, peer acceptance of the direct effects on intelligent is reduced to 1.4292 from 1.4978. Consequently, primary school students'friendship quality partly mediates the relationship between peer acceptance and intelligence on individual level. Mediator effect is ab( × )=7.18%,mediator effect size is ab/(ab+c')=4.78%.We adopt the same procedure as above on other dimensions of personality. The conclusion shows that:(1)In class level, the average level of friendship quality in class has a direct effect on extraversion, pro-sociality, conscientiousness, emotional stability. The average level of peer acceptance in class has a direct effect on emotional stability.(2)In individual level, peer acceptance has a direct effect on the five dimensions of personality(intelligence, extraversion, pro-sociality, conscientiousness and emotional stability). Primary school students’ friendship quality partly mediates the relationship between peer acceptance and personality (intelligence, extraversion, pro-sociality, conscientiousness).