The impact of climate change on water resources security is a challenging issue with widespread concern globally. It is as well the great strategic issue in the national sustainable development of China. Based on a wide review of related research, it is concluded that the research of climate change impact on the water cycle is one of the most exiting research perspectives in the study of relationship of climate change and water science. Due to the serious water resource situation plus climate change influence, the challenge and opportunity of the basic research work in the climate change impact on water resource were given. The climate change and water cycle study is the international forefront in the area of climatology, meteorology and hydrology. The detection and attribution of water cycle components change have become the international challenging problems, as well as the quantitative analysis and prediction of the uncertainties in a hydrological system; the research of water cycle response to climate change is developing from offline hydrologic simulations to coupling climate change with hydrological dynamics; study of the water resources vulnerability has become a key problem to deal with climate change and secure the water resources security. In the circumstances of the climate change, it is necessary to reexamine the hypotheses in traditional hydrological theories, as well as the spatial variability, uncertainty and hydrological extremes in regional hydrological studies. Carrying out the research of climate change impact on water resource and adoption measures is one of the  biggest scientific problems of water sciences and water resource in the 21 century. 