As one of the longest and largest rivers on Earth, the Mekong river flows along six countries. Mekong River Basin is a home of various plants, animals and fish as well as providing great economic value to supply for more than sixty million people living along it. Nevertheless, the natural environment and local communities are on the verge of alarming danger because of huge hydropower dam constructions. The development of big constructions and human activities without the careful examination lead to the high tension among riparian states. In the large picture, the Mekong river sub-region now shifted into the playifng ground of riparians and powers. By applying the hegemony and power theory to transboundary water analysis as well as non-traditional security perspectives, the purpose of the article is to draw the current situation of power game playing, hydro hegemony challenged from examining the impacts of hydropower constructions to searching for water influence in in Mekong sub-region.