Water pollution emergency incidents have become an important issue in water safety management. In view of the fact that traditional assessment methods cannot balance the problems of ambiguity and randomness in the evaluation system, the author applied the normal cloud model to the safety assessment of water pollution emergencies, and the mixed cross-weighting(MCW)-normal cloud evaluation model was established to carry out the water pollution emergency safety assessment of the Heihe Catchment in Qilian Mountains , Zhangye from 2012 to 2017. We selected 15 indicators to build an indicator system and grading standards using the PSR model, and adopted the MCW-normal cloud model to determine the weight and membership, respectively. And then, the values of the weight and membership were combined to evaluate the safety level of water pollution emergencies. Finally, the results of the assessment were compared and analyzed with those of the improved close value method and the fuzzy comprehensive evaluation method. The results showed that the safety level of water pollution emergencies in the Heihe Catchement of Zhangye in 2012 was at Class II major risk, and it was at Class III in 2013-2017. The evaluation results are basically consistent with the improved close value method and the fuzzy comprehensive evaluation method. This method can effectively realize qualitative and quantitative transformation, and is feasible for the safety assessment of water pollution emergencies. Therefore, it can be used as a new safety assessment model for water pollution emergencies.