The invesigation and evaluation of water resources is an important basic work for the comprehensive planning of regionalwater resources， the early-phase demonstration of water structure construction,the management and protection of water resource,the construction of ecological civilization，and the development of economy and society. Therefore, it is of great social-economicsignificance to summarize and analywe the resuls of regional water resources investigation and evaluation in different periods.Basedon the previous two water resources investigations and evaluations in Qinghai Province, this paper enriched the contents of theevaluation, and improved the evaluation method. This paperalso analyzed the main differences in the process of the threeevaluations, and discussed the diffcult problems in the evaluation of Qinghai Lake Basin and Qaidam Basin,considering the poordata condition in the Northwest China.