Dry excavation is a vital dredging method to improve the surface water environment quality of ditches in the Nanhan embankment.In order to investigate the effect of the surface water environment quality，water environmental capacity，and the eutrophication index of water by dry excavation dredging.Taking the ditches in Nanhan embankment as the research object，the water sample，water environment capacity，and eutrophication evaluation results of the ditches before and after dredging were analyzed and discussed.The result shows：1）The surface water quality becomes worse with the completion of dredging.2）The water environmental capacity of the ditch with high ferocity index increased from 13.99 t/m before desilting to 38.88 t/m one month after desilting.The water environmental capacity of TN and TP increased 2.8 times and 2.7 times，respectively.3）Before dredging，the surface water cultivation and drainage area in the ditch inside the embankment reached the degree of severe eutrophication；after dredging，the ΣTLI value increased with the completion of dredging time.The main reason for the decreasing control effect of dredging by dry excavation is the input of agricultural non-point sources and aquaculture sewage.Therefore，the realtime monitoring of surface water in the embankment should be carried out，and new dredging projects should be started in time.The results can provide a theoretical basis for dredging treatment of rivers or ditches.