With the Kenli District of Dongying City used as an example, a study on the optimization of crop structure in the Yellow River Delta was conducted. The water demand, effective precipitation, and leaching water demand of main crops in each growth stage and the whole growth period were calculated, and water surplus and deficit of different crops were analyzed. The results show that crops are ranked in the following ascending order according to the supplementary irrigation water demand: corn, cotton, wheat, and rice; corn has the lowest degree of water deficit, and thus, the planting area of corn can be increased appropriately or the rotation of winter wheat and summer corn can be replaced by planting corn(spring corn and summer corn)twice a year; the planting area of cotton can be reduced in moderately and slightly saline-alkali land, and drainage reuse or brackish water irrigation can be used for cotton planting because of its good salt tolerance; irrigation water and water for salt washing can be mixed for rice planting, and then, the slightly saline-alkali land improved by rice planting can be used for corn and wheat planting.