The water cycle is intensified,variation of hydrological processes and water resource become more complicated in mountainous areas under global climate change. Understanding the water cycle of mountainous watersheds and its relationship with climate,vegetation and soil in the changing environment is the key issue of both global change and sustainable development of human society. Based on the study of the forest spatial heterogeneity effect on evapotranspiration,soil moisture,water balance and the coupled relationship between water and carbon in Gongga Mountain,a brief review was done to introduce the research work and scientific results in Gongga Mountain. Furthermore,three key scientific issues of mountainous hydrology under complex mountainous regions is put forward: ( 1) the research of vegetation-hydrology-soil continuum under SPAC system should be carried out systematically; ( 2) a multi-scale comprehensive research work of ecological hydrological process need to be done; ( 3) the hydrological model that can simulate the water cycle more accurately in complex mountainous regions still need to be developed.