A trimaran usually consists of a main hull and two side hulls which has already been an important type of high-performance vessels. In order to reduce its total drag at different speeds for the need of saving energy and reducing pollution, the hull form optimization solver OPTShip-SJTU is used, and the spacing of side hulls and the shape parameters of the main hull can be changed and regarded as optimization design variables. Furthermore, the total drag of the trimaran is evaluated based on the potential flow theory after verifying the reliability of the potential-flow-based NMShip-SJTU solver. After evaluations of new sample hulls created by Optimal Latin Hypercube Sampling method, Kriging surrogate models are then constructed and validated to save the computational cost. Finally, a multi-objective optimization program is implemented to obtain the optimal hulls, and the selected typical optimal trimarans are further analyzed to ensure the optimization effects.