The ideal superstructure means that the superstructure does not bend when the hull is bent， and the normal stress of the superstructure is consistent in the direction of height. Different from the strong superstructure and the light superstructure， the stress level of the ideal superstructure is close to the main deck， which can maximize the utilization of material strength. In this paper， a typical oil tanker is taken as the research object. Based on the composite beam method， considering the influence of shear hysteresis effect， the design method of ideal superstructure is discussed. According to the section characteristics of superstructure， the length of ideal superstructure is explored. Based on the theoretical formula of the ideal superstructure， the design length of the ideal superstructure is obtained according to the parameters of the transverse section of the ship. After the theoretical design scheme of the ideal superstructure is obtained， the stress distribution law of the deck of the ideal superstructure is verified by the finite element method. The verification results show that the normal stress level of the superstructure is close to the main deck， which can provide reference for the design of the early ideal superstructure. Finally， the deck thickness of the superstructure is adjusted to save materials and reduce the center of gravity.