Abstract: There are many cracks in concrete structure of Shuikou hydropower house such as slab of generator floor, bent frame column and joins between bracket support and slab. Based on photographic data, image correction and mapping of cracks, the spatial distribution characteristics of cracks were obtained. Then combined with load conditions and structural characters of Shuikou hydropower house, the analysis result showed the cracking reasons were dynamical forces caused by water flow impulse pressure of spiral case and mechanical vibration of generating units.