The utility model discloses a FLNG upper portion module buttress system, including setting up first, second, third and the fourth buttress body at four angle points in upper portion module bottom, the diagonal is arranged first buttress body with fourth buttress body, the upper surface and the upper portion module pillar sliding contact of one of them buttress body, the upper surface and the upper portion module pillar fixed connection of another buttress body, the diagonal is arranged second buttress body with third buttress body, the upper surface and the upper portion module pillar sliding contact of one of them buttress body, and be provided with the restriction the baffle that the upper portion module was moved along width of a boat direction, the upper surface and the upper portion module pillar sliding contact of another buttress body, and be provided with the restriction the baffle that the upper portion module was moved along captain's direction. The utility model discloses an arrangement form spacing relatively can furthest reduces ship motion and to the influence of module, improves holistic operating efficiency coefficient of FNLG and factor of safety.