The utility model provides a semi-submerged platform and lower body thereof, said body down includes two bow stern sections and an interlude, and two bow stern sections are connected respectively at the fore-and-aft both ends of interlude, serve as reasons on the vertical structure of middle part to both ends width convergent of said bow stern section, the maximum breadth department of bow stern section is through curved surface rounding off to outer end, and the outer end tip of bow stern section forms the cambered surface, the maximum breadth department of bow stern section with interlude curved surface rounding off is connected, the maximum breadth of interlude is less than the maximum breadth of bow stern section. The utility model discloses a streamline structure's lower body is favorable to reducing the towing of semi-submerged platform and the resistance that navigates certainly, when navigation or traction navigate by water the operating mode certainly, reduces the fuel consumption of platform host computer or tow boat host computer, and then has reduced the operating cost. Furthermore, the utility model discloses still can make hanging down of platform swing motion amplitude response operator can reduce, has improved the platform and has hung down and swing the performance.