Abstract: Combined with an in-stream hydropower house, cracking characteristics of reinforced concrete spiral case were analyzed by a nonlinear finite element method, and effects of steel fiber-reinforced concrete and epoxy mortar on concrete crack control are discussed. The results indicate that water head endured by this spiral case is not high, but owing to the large size of its orifices, cracks are very likely to appear in the intersections of its roof, floor and sidewall and on the generator pier. For a large-scale concrete spiral case, high strength concrete or steel fiber-reinforced concrete can reduce the extent of its concrete damage, while they have little effects in prevention of its cracking and they will, on the contrary, induce problems of high hydration heat and complicated construction technology. Thus, adoption of concrete with lower strength is more rational if combined with an effective control on crack width within a certain allowable range and a measure of seepage prevention. To reduce seepage, steel liner and epoxy mortar coating on the inner wall of spiral case are effective, and for crack control, a beneficial measure is to allow the steel liner and epoxy mortar to carry a certain part of the load. During practical operation, aging and spalling of the epoxy mortar are the problems unsolved yet, so steel liner is better and reliable in terms of durability.