The invention discloses a structure for preventing a brittle fracture of a main hull. A main body of the structure is a container ship; a longitudinal continuous hatch coaming and a longitudinal continuous hatch top plate are arranged on an upper deck of a broadside dual-shell of the container ship; the longitudinal continuous hatch coaming and the upper deck are positioned at the middle part of a hull of the container ship; the longitudinal continuous hatch top plate is connected in a welding mode to the top end of the longitudinal continuous hatch coaming; the longitudinal continuous hatch coaming and the upper deck adopt extremely thick steel sheets with the crack arrest characteristic; by verification of a double tension test or an ESSO test the crack arrest characteristic of the extremely thick steel sheets meets the requirements of the following formula: a crack arrest temperature CAT is lower than or equal to minus 10 DEG C, or at a temperature of minus 10 DEG C, a crack arrest toughness Kca is greater than or equal to 6,000N/mm<3>/2. By triple guarantee, the risk of the brittle fracture of the main hull structure of the container ship can be reduced to a very low degree, which is helpful for obviously improving security of the large-scale container ship.