Abstract: By means of test research, a small sized inlet with a symmetrical bell-mouth form instead of traditional large sized one will be adopted for the TGPs hydropower station. The flow-pattern of the small inlet not only can meet desired requirements and its water head loss is less than that of large one, but also it can improve stress state within dam body. This kind of small inlet may be served as valuable reference for other similar hydropower station. It is an effective method for improving test precision that the water head loss tests of hydropower station inlet section are performed by increasing discharge or raising reservoir water level.