The invention discloses semi-submersible ships capable of being combined. Each semi-submersible ship capable of being combined comprises a ship body deck and a forecastle arranged on the ship body deck, wherein the forecastle on one side of the main center line of the ship body deck is a movable forecastle capable of being detached and moving, and the movable forecastle can move to any position of the spacious deck. The invention further discloses a combined type semi-submersible ship which is formed by integrally connecting one side of the ship body deck of one semi-submersible ship capable of being combined and one side of the ship body deck of the other semi-submersible ship capable of being combined. The movable forecastles are moved to one sides of the ship body decks respectively to be close to corresponding fixed forecastles, so that the deck formed by the two semi-submersible ships capable of being combined passes through the front portion and the back portion of a stern. The combined type semi-submersible ship has the advantages that the requirement for conveying larger unconventional heavy pieces can be met, and meanwhile economic cost can be taken into consideration; the combined type semi-submersible ship can be divided into the two conventional type semi-submersible ships in the operating period when the unconventional conveying is not needed; accordingly, operating cost is reduced.