The purpose of this study was to investigate the sex and grade differences on self-disclosure and autonomy while college students were developing mature interpersonal relations. Subjects were 352 college students. Questionnaire was used as the research method. Two-way ANOVA was used for data analysis, sex and grade were independent variables, self-disclosure (including the width and deep of self-disclosure) and autonomy (including emotional independence, instrumental independence, and interdependence) were dependent variables. The results were: (1) In the width of self-disclosed wider than freshman、sophomore and junior ones when interacted with peers, but the there was no grade differences of female students. In the deep of self-disclosure, there was also an interaction effect between sex and grade, there were no grade differences of male students, but senior female students disclosed deeper than freshman、sophomore and junior ones when interacted with peers. (2) In the emotional independence of autonomy, sex differences were not significant but grade differences existed, the emotional independence of freshman、sophomore and junior was higher than senior. There was an interaction effect between sex and grade on the emotional independence, the emotional independence of freshmant、sophomore and junior male students was higher than senior ones, the emotional independence of sophomore and junior female students was higher than senior ones. In the instrumental independence of autonomy, sex differences were not significant but grade differences existed, the instrumental independence of senior was higher than sophomore and junior ones, the instrumental independence of sophomore and junior was higher than freshman. There was an interaction effect between sex and grade on the instrumental independence, the instrumental independence of senior male students was higher than freshman、sophomore and junior ones, the instrumental independence of senior、junior and sophomore female students was higher than freshman female ones. In the interdependence of autonomy, the "avoidance of mutual interference and competition" factor of interdependence of freshman was lower than sophomore、junior and wenior.