Abstract: This study mainly aims at the problem that there are numerous factors and uncertainties in dam breach environment. The index system and corresponding grade classification standards were established based on the comprehensive analysis of seven environmental factors of dam breach, such as channel morphology and water environment. Considering that set pair analysis deals with the certain and uncertain problems in the evaluation process well, in order to fully express the identity, difference and opposite relations among sets, the original connection number is extended to five element connection numbers and its difference component coefficient is further described in combination with triangular fuzzy number theory. Consequently, the model coupled with set pair analysis and triangular fuzzy number for assessing environment impact of dam breach was established. Taking Shaheji Reservoir dam as an example, the evaluation results of the established coupling model were compared with those of set pair analysis and fuzzy mathematics, which shows that the model is reasonable and effective, hence providing a new way for dam breach environmental impact assessment.