Abstract: In order to validate the relations between the root-water-uptake and the root nitrogen mass, and optimize the salinity stress reduction function, a field experiment was designed to estimate the root-water-uptake rate distributions of winter wheat and discuss the relationship between the maximum root-water-uptake rate and the root nitrogen mass density. The relationship was used to establish a root-water-uptake model, optimize the salinity stress reduction function, and simulate the root-water-uptake dynamics under salinity stress. The simulated root-water-uptake rate distributions were comparable with the estimated values using the inverse method. The results showed that the linear relationship between root-water-uptake rate and root mass nitrogen was applicable in optimizing the salinity stress reduction function and establishing the root-water-uptake model under salinity stress.