Urban river ecological governance is an important aspect of the construction of ecological city, and the performance level of a project during the operation period is the key to the long term comprehensive benefits it brings after the completion. We selected 18 evaluation indexes from four aspects of organization management, supervision management, engineering management and comprehensive benefit management, and constructed the performance evaluation index system of urban river ecological governance project in operation period. Then a performance evaluation model of urban river ecological governance project in operation period was established based on combination ordered weighted averaging(COWA)-grey fixed weight clustering method. The performance level of a river ecological governance project in operation period in Xi’an was evaluated using this model. The results show that the comprehensive performance of the project during the operation period is evaluated as 7.806, which is classified as “good”. Among the indicators, the performance level of secondary indicators of project management is the highest, and the result is “excellent”. The performance level of the other three secondary indicators is “good”, which is basically consistent with the actual situation of the project. The results can reflect the performance level of urban river ecological governance projects in operation period objectively and can provide some reference for the improvement of their management.