Background:　Self-disclosure　is　related　to　one＇s　interpersonal　relationship　and　personal　physical　and　mental　health　as　well,　and　in　the　recent　forty　years,　it　has　been　a　very　important　research　subject　in　the　fields　such　as　social　psychology,　clinical　psychology,　and　interpersonal　relationship,　etc.,　and　studied　extensively　abroad.　How　is　self-disclosure　related　to　the　personality　characteristics,　loneliness,　and　mental　health　in　Chinese　college　students?　Objective:　To　understand　the　relationships　of　self-disclosure　with　personality　characteristics,　loneliness　and　mental　health　in　Chinese　college　students,　and　provide　guidance　for　these　students　to　adapt　themselves　to　interpersonal　relationship　better　and　promote　their　psychological　health.　Design:　A　cross-sectional　study.　Setting:　Department　of　Social　Science,　School　of　Social　Science,　Beijing　University　of　Technology;　Developmental　Psychology　Institute　of　Beijing　Normal　University.　Participants:　Totally　424　college　freshmen　and　first-year　postgraduates　(consisted　of　224　males　and　200　females),　aging　from　17　to　37　years　with　a　mean　of　(22　±　3)　years,　were　selected　from　a　university　of　technology　in　Beijing.　Interventions:　The　test　was　carried　out　with　the　cluster　sampling　method.　Group　measurement　was　carried　out　with　Jourad＇s　Self-Disclosure　Questionnaire　(JSDQ),　Revised　Eysenck　Personality　Questionnaire　Short　Scale　for　Chinese　(EPQ-RSC),　Loneliness　Scale　(UCLA)　and　Self　Check-list-90　(SCL-90).　Main　outcome　measures:　Self-disclosure　and　its　relationship　with　personality　characteristics,　loneliness　and　psychological　health　in　college　students　were　measured　with　JSDQ　and　EPQ-RSC,　JSDQ　and　UCLA,　JSDQ　and　SCL-90.　Results:　Self-disclosure　was　significantly　positively　related　to　extraversion　(r　=　0.29,　P　＜0.01)　and　inversely　to　loneliness　(r　=　-0.36,　P　＜0.01)　in　these　college　students.　Loneliness　was　more　strongly　felt　in　students　with　low　level　of　self　disclosure　than　in　those　with　high-level　self-disclosure　(r　=　-0.36,　P　＜　0.01).　Self-disclosure　showed　significant　inverse　relation　to　the　depression　factor　in　SCL-90　in　these　students　(r　=　-0.16,　P　＜　0.01).　Conclusion:　The　variation　of　the　levels　of　self-disclosure　has　certain　relations　to　loneliness　or　to　personality　characteristics　and　emotional　experience.