The invention discloses a method for calculating a ship weight longitudinally distributed load density. By adopting the method, the situation that partial weight losses or distortion of equipment at aship bow / stern can be avoided, so that weight distributed load density is more reasonable and accurate. According to the method for calculating the ship weight longitudinally distributed load density, the ship bow and the stern can serve as complete standard theoretical station distances correspondingly, 20 standard theoretical station distances in a traditional method are expanded to be 22 standard theoretical station distances, and then weight of each equipment or goods on a ship is equivalently distributed on the standard theoretical station distances in theoretical station distance ranges where the equipment or the goods are located according to a static force equivalence principle; and the weight distributed in the ship bow standard theoretical station distance and the stern standard theoretical station distance is converted into two standard theoretical station distances adjacent to the ship bow standard theoretical station distance and the stern standard theoretical station distance, and finally weight distribution of the 20 standard theoretical station distances of a hull, namely, the ship weight longitudinally distributed load density, is obtained. Partial weight lossesor distortion of the equipment at the ship bow / stern is avoided, and weight distributed load density is more accurate.