The objectives of this research were to investigate the factors that affected social carrying capacity and to establish the model of social carrying capacity in the case of the white water rafting on the Hsiukuluan River. The finding has shown that crowding perception is more suitable than satisfaction as an indicator for forecast of social carrying capacity. The major concerns about social carrying capacity occured at rest area and terminal. Besides use level, perceptions of overuse impacts as well as perceptions of visitors' behavior would affect their crowding perceptions. Improving facilities and regulating visitors' behaviors would increase the social carrying capacity.