Abstract: Based on the powerhouse of a pumped-storage power station, a three-dimensional FEM model is established. Compared dynamic calculation with modal experiment, the reason of the cracks by the vibration of the powerhouse is analyzed. Based on the current model, the modal calculation and transient calculation of thick slab strengthening plan of the powerhouse are carried out. The results indicate that thickening concrete slab can increase the rigidity of the powerhouse and decrease the frequency a litter; and the part vibration can be decreased obviously. The dynamic stress of the strengthening powerhouse is less than that of the current powerhouse, but some points are opposite.