Two studies were conducted using dictator games and real-life scenarios to explore the psychological mechanisms of excessive third-party punishment influenced by group identity. As a result, it was found that group identity as individuals who are consistent with the victim's group identity will result in excessive third-party punishment for violators; The threat of social identity partially mediates the impact of group identity on excessive third-party punishment; The moderating effect of group identity on excessive third-party punishment is manifested in individuals with high levels of group identity making excessive third-party punishments.