The purpose of our study is to investigate whether there is a difference in the personality traits and related personality traits between the only child and non?only child college students. The sophomores from three universities in Jiangsu Province were selected and investigation was conducted using PID?5 and general data sheets. The research found that there were no statistically significant differences between the only children and non?only children in the five personality dimensions of negative emotions， separation， confrontation， disinhibition， and psychosis （t=-0.374~0.140，P>0.05）. In terms of intimate personality traits， the difference between the only child and non?only child is statistically significant （t=-0.736，P<0.05）. In 24 other items of personality traits， the difference between the only child and non?only child were not statistically significant （t=-2.525~1.095，P>0.05）. The conclusion is that there was a difference in the personality trait of avoiding intimacy between the only child and the non?only child. This study suggested that we should pay more attention to students’ interpersonal communication and give students more encouragement and support in university psychological education.