As an important part of natural resources, water resources and its cycle process have been gradually disturbed by many disturbers such as changed climate and increased human activities, etc. The dynamic change of water resources in river basin and its sensitivity to weather and human activity make water cycle become a very complex process. Thus, it is necessary to assess water resources and study the evolution law of water resources under changed climate and human activities. Aimed at the characteristics of water cycle, two aspects are researched in this dissertation: first is to establish the principle and methodology of water resources comprehensive assessment, and the second is to study the evolution law of water resources.Research progress of water resources assessment and water resources evolution is summarized and the main problem in them is also analyzed. It is point out that the distributed hydrological model can provide technique support for assessing water resources and understanding water resources evolution in river basin. Furthermore, research progress of distributed hydrological model as a study measure of water science is also summarized. The principle and methodologies of comprehensive water resources assessment is established based on the predecessor experience, which include hiberarchy, avail of cycle and dynamic assessment of water resources. The evolution characters of water resources are discussed and then the analysis models are established to study the basic special and temporal principle of water cycle factors, the models are R/S method for randomicity, chart analysis for periodicity, Kendall method for tendency, T method for abruptly change, and orderly clustering for changing point testing. Scene analysis method is applied based on distributed hydrological model to study the effect of the main driver factors such as climate, underlying surface and water use condition on water cycle.The dualistic water cycle model, combining the WEP-L distributed hydrological model and centralized water resources allocation model, is introduced based on the analysis of natural-artificial water cycle system.The dualistic water cycle model as a case study with Yiluo river basin is established. The four high sensitive parameters with maximum depression storage of land surface, conductivity of aquifer, maximum soil moisture content, conductivity of river bed are attended the optimize calculation in order to verify the model. The result manifest that the model structure is rational and the validate result is ideal. Thus the model is suitable for the Yiluo river basin. Applying the model, the comprehensive assessment of water resources is studied which will make an fully scientific explain for the water resources. Furthermore, the evolution of water resources of 45 years in Yiluo river basin is studied to gain the main characteristics. The effect