The invention provides a ship mainframe cross brace reinforcement structure and a ship, and relates to the technical field of ship construction. The ship mainframe cross brace reinforcement structureand the ship are designed to solve the problems that existing ship mainframe cross brace reinforcement structures cannot effectively enhance the transverse rigidity of joints of cross braces, correspondingly mainframe vibration cannot be effectively suppressed, and the layout of pipelines and passing of crews are inconvenient. The ship mainframe cross brace reinforcement structure is fixed to cross braces, a longitudinal passage is formed between the ship mainframe cross brace reinforcement structure and a longitudinal bulkhead, the ship mainframe cross brace reinforcement structure includes partial longitudinal bulkheads, and the partial longitudinal bulkheads are fixed to the main structure of the ship. The ship includes a ship body and the ship mainframe cross brace reinforcement structure. According to the ship mainframe cross brace reinforcement structure and the ship, the transverse rigidity of joints of the cross braces can be enhanced, and the technical problems that layout ofthe pipelines and passing of the crews are inconvenient are solved while the vibration of a mainframe is effectively suppressed.