According to the characteristics of bulb-type tubular unit，the powerhouse overall stability and structural stress have been respectively analyzed by using the material mechanics method and three-dimensional finite element method. Reasonable layout and structure design have been carried out for the powerhouse by properly setting the locations of water-stops between joints，as well as the foundation treatment.The satisfactory results are obtained for the powerhouse design，and the overall layout and structural design of powerhouse are reasonable，safe and economical.