According to the actual water quality monitoring data in the first phase project of eastern route of the south to north water diversion project during water transfer test of 2013 in water monitoring section of trunk route, the paper analyzed the state of water quality change and quality change characteristics each section before and after water test during water so as to provide a reference for the continued operation of the eastern route of south to north water diversion project and the subsequent construction.The result shows that before and during water diversion test, the water quality each monitoring section reached the II～III level according to the Chinese surface water quality standard (GB3838-2002);the variation trend of dissolved oxygen along the path is not obvious;all of permanganate indexes express a clear up trend; ammonia nitrogen express a clear down trend before water diversion experiment, but express a clear up trend during water diversion experiment.The data also show that in order to guarantee the safety of water quality in long-term operation,it is necessary to take measures so as to thoroughly improve the water quality along the tributaries of the canal.