This study is about the sediment distribution change characteristics using a two-dimensional model and selected the representative grain diameter by using the results of riverbed changes simulation using suspended sediment concentrations before and after river maintenance and river bed materials and compared and reviewed the results of simulating the resulting river bed changes. A analysis target river is Daecheon located in Gyeongju, Gyeongbuk and suspended sediment survey results showed that the suspended sediment grain diameter before and after river maintenance was found not to show a big difference, the average grain diameter before and after river maintenance 0.0606mm and 0.0591mm, respectively but it was analyzed that a significant difference occurs, the highest suspended sediment concentration before ana after river maintenance 58.6mg/l and 140.7mg/l, respectively. Also, when applying the suspended sediment concentration measured in the river bed state before river maintenance and applying suspended sediment concentration measured in the river bed state after river maintenance, various suspended sediment concentration was analyzed to generate the differences of erosion and sedimentation and based on the differences by the left bank, middle, right bank, maximum erosion 0.0028m and maximum sedimentation 0.0043m, maximum erosion 0.0013mm and maximum sedimentation 0.0027m, maximum erosion 0.0084m and maximum sedimentation 0.0062m of the difference in erosion and sedimentation were shown at the left bank, middle, right bank, respectively. Riverbed changes appear differently depending on river maintenance and the proper maintenance of the river is determined to be made when adopting an appropriate analysis method according to the riverbed shape during river maintenance and management before and after river maintenance.