The invention discloses a door type two-way movement marine drilling rig substructure. The substructure comprises two parallel support frames, two symmetrical top supports are installed on the sides where the two support frames are close to each other, two symmetrical moving supports are hinged to the ends where the two top supports are close to each other, and the ends where the two moving supports are close to each other are hinged. Two symmetrical installation supports are installed below the ends where the two top supports are close to each other, butt-joint rods are installed on the sides, where the two installation supports are close to the top supports, in the length directions of the installation supports at equal intervals, and sliding rails are installed on the sides, where the butt-joint rods are close to the installation supports, in the length directions of the butt-joint rods. The sliding rails are connected with the installation supports in a sliding mode through sliders, and supporting rods are hinged to the lower sides of the ends where the butt-joint rods are close to the moving supports. According to the door type two-way movement marine drilling rig substructure, the drilling rig substructure is changed into an expandable and folding structure from a conventional fixed structure so that the drilling rig substructure can contract, convenience is brought to the transportation of the drilling rig substructure, and spaces are saved.