Abstract： Objective To understnad the defense mechanisms of patients with borderline personality disorder (BPD) and to explore its relationship with childhood abuses.Methods One hundred and forty-two outpatients with BPD (group A),63 outpatients with other personality disorders (group B) and 20 outpatients without any Axis Ⅱ diagnoses (group C) were enrolled and completed Chinese versions of the Childhood Experience of Care and Abuse Questionnaire (CECA.Q) and the Defensive Style of Questionnaire (DSQ).Multivariate analysis of variance and Pearson correlation analysis were used for data analysis.Results Compared to group B and C,the score of defense mechanisms reported by group A were significantly increased in all eight premature defense mechanisms,such as projection(F =26.5,P ＜ 0.05),passive aggression (F =18.1,P ＜ 0.05),acting out (F =28.3,P ＜ 0.05),complaint (F =16.7,P ＜0.05),fantasy(F =16.3,P ＜ 0.05),splitting (F =28.8,P ＜ 0.05),withdrawal (F =8.3,P ＜ 0.05),somatization(F=7.6,P ＜ 0.05),and part of the middle defense mechanisms,such as omnipotence-devaluation(F =9.2,P ＜ 0.05),isolation(F =4.7,P ＜ 0.05) and identification (F =10.0,P ＜ 0.05).At the same time,the BPD patients got lower scores in the mature defense mechanisms,such as sublimation (F =4.1,P ＜ 0.05) and repression(F =3.9,P ＜ 0.05).Those who experienced physical abuse use more complaint (F =6.9,P ＜ 0.05),denial mechanisms (F =5.2,P ＜ 0.05) and less anticipation one (F =4.6,P ＜ 0.05).Those who experienced sexual abuse use more somatization (F =4.4,P ＜ 0.05) and isolation mechanism (F =3.6,P ＜ 0.05).Conclusions BPD patients would like to use more immature and middle defense mechanisms and less mature ones.Emotional,physical and sexual abuse from parents and other adult care takers have a correlation with immature defense mechanisms,which indicates the importance of care about parental rearing patterns and mental health of children.