Abstract: Aimed at farmland irrigation-crop-cultivation systems,a new model was developed for optimization of agricultural cultivation management,encompassing the factor of water quality and some others. With the maximum benefit of a farmland system being its target function and the traditional irrigation volume and the limitation of the use of pesticides and fertilizer being its restraints, this model also takes into account the influence of concentration of the pollutants in farmland runoff and river flowon the system, in optimizing crop cultivation mode for the farmland system. A case analysis shows that the existence of the restraint of water quality leads to a variety of farming modes for different farmlands. At the same time, for an optimal farming mode, the concentrations of nitrogen and phosphorus in the river flow are allowed to reach as high as the limit set for Grade III of the GB 3838-2002 “Standard for Surface Water Environment Quality”. So that, the model can not only provide some scientific basis for rational utilization of agricultural water resources, but also offer some referenceto decision makers in designing scientific farming modes.