Objective:To explore the mediating effect of loneliness on the relationship between interpersonal adaptation and mobile phone addiction in college students.Methods:Totally 368 college students (176 males and 192 females )were surveyed with the College Student Adaptability (CSAI),University of Califomiaat Los Angels (UCLA)and Mobile Phone Addiction Index (MPAI).Then AMOS18.0 was used to establish structural equation modeling (SEM)among interpersonal adaptation,loneliness and mobile phone addiction,and test the mediating effect of loneliness on the relationship between interpersonal adaptation and mobile phone addiction in college students.Results:The MPAI scores were significantly higher in the low interpersonal adaptation group (the score of CSAI less than 21 )than in the high interpersonal adaptation group (the score of CSAI higher than 32)(P<0.001).The scores of interpersonal adaptation were negatively correlated with scores of loneliness and mobilephone addiction (r =-0.71,-0.25,P﹤0.01).The scores of loneliness were positively correlated with scores ofmobile phone addiction (r =0.32,P ﹤ 0.01).College students'interpersonal adaptation did not have significantnegative predictability for mobile phone addiction (β=﹣0.08,P =0.32),but it had significant negative predictabilityfor loneliness (β=﹣0.71,P <0.001).Loneliness had significant positive predictability for mobile phone addiction(β=0.29,P <0.001).Conclusion:The results show loneliness completely plays a mediating effect betweeninterpersonal adaptation and mobile phone addiction.