A rolling-mat closure hydropower station building method uses the caisson technology to build a dam in running water, and uses a rolling-mat closure method to cut off the running water, thus saving diversion, cutoff and cofferdam steps, fast building a hydropower station, shortening a work period, reducing investment, reducing excavation amount, and providing environmental protection effect; the method is applied to build a cross flow hydropower station, electricity can be generated according to water quantity, and no water reservoir is needed; like Gezhouba hydropower station in Changjiang river middle reaches, with capacity of 2.71 million kilowatt, the land acquisition can be reduced without taking farmland and villages, and the hydropower station can be fast built for power generation; the method can be applied to a river dam port so as to block the opening; the method can be applied to any river for building hydropower stations, can build a high dam hydropower station as wall, thus having very well prospect, fast providing water power electricity power for one-belt-one-road infrastructure, helping various nations to fast develop, and allowing SINOHYDRO to win completions with foreign country hydropower groups.