Shipbuilding industry is an industry that is always evolving over time. One of the problems of the shipbuilding industry is a large shipbuilding costs, due to hull shape that requires the bending process to adjust to the shape of the ship. To overcome these problems, a type of vessel designed using the flat surface hull to reduce the production cost of the ship. The purpose of this thesis is to analyze the stability of the designed fast ship that applies a flat surface hull. The objective of this paper is to carried out stability analysis of flat surface hull by simulation through the MaxSurf application. The main dimension of the flat surface hull that used in this study are length overall is 13.9 meter, beam 3.4 meters, and the draft is 0.85 meter. Maxsurf stability is used to find the GZ curve of ships with nine different loading conditions. The result shows the stability if flat surface hull meet the all criteria by International Maritime Organization with angle of maximum GZ above 25 deg.