The invention relates to a semi-submerged small-waterplane-area mobile platform type marine nuclear power station belonging to the technical field of offshore engineering equipment and comprising a deck, small-waterplane-area upright posts, bottom hull shells, strut rails, an anchor chain, a nuclear generating device peripheral watch box, an electric power pylon, a revolving ring, an anchor, a nuclear reactor and a converting station, wherein one ends of the eight small-waterplane-area upright posts are respectively arranged on the two bottom hull shells, and the other ends are fixedly connected with the bottom surface of the deck; both ends of the four strut rails are respectively fixedly connected with the side surfaces of the two bottom hull shells; and the nuclear generating device is arranged on the deck. The marine nuclear power station can be fixed in a certain sea area for long-term work and can also be towed by a tugboat to arbitrarily move to change the workplace. The invention has high generating capacity, long service life, high safety, fuel saving, small resistance in towing and high stability, and can endure severe sea conditions. The invention has important scientific research value, important industrial application prospect as well as military and national defense values and obvious economic benefits and social benefits.