The purpose of this paper is to research the relation between peer relationship and sport-confidence among the collegiate volleyball players. Participants in the study are the players in 2017 University Volleyball League in the northern area of Taiwan. Consequently, there are five results. First, the average of the measurement on peer relationship of male players is higher than that of female players. Second, the peer relationship between the players who advance to the final is better. Third, the more days the players practice together, the better the peer relationship is and the higher the sport-confidence is. Fourth, the players who are underweight (BMI<18.5) are more confident that the players who are overweight (BMI≧24). Fifth, peer relationship and confidence are positive correlation, and it reaches the significant level. The closer the relationship among players is, the stronger the confidence is.Finally, the author hopes that the analysis of this study would provide trainers and players with the application of teaching and training.