To optimize a hull form of a twin-screw vessel with a block coefficient of about 0.9 and velocity Fr number of about 0.1, to reduce its resistance. Firstly, numerical simulations of the parent hull form were carried out at design draft and design speed by using CFD methods to analyze the dynamic pressure distribution, wave pattern, streamlines around the hull, etc. and determine the optimization direction. Then, under displacement and geometrical constraints, modifications were made to the bow entrance angle and bow shape to reduce wave resistance and make pressure distribution more uniform. Then the transom length at the aft was increased and the run angle in longitudinal sections was reduced to avoid possible flow separation. Around the stern fins, fullness was increased and run angle decreased to refine and fair the tail-fin shape, to avoid shoulder interference. After several optimization iterations, while satisfying all constraints, the total resistance was reduced by over 5%, free surface wave making was significantly reduced, bow pressure distribution was more uniform, and no obvious flow separation occurs near the stern. The hull form optimization achieved the goal of reducing resistance and saving energy.