Abstract: [Objectives]To study the influence of steps on direct navigation performance in calm water of stepped double M-hull craft, [Methods] four double M-hull crafts are established by transforming a standard geometry modeldefined original ship and setting steps at the position of 0.5L and 0.25L. By verification and validation, an optimum grid scheme is obtained. Using the validated grid scheme, numerical simulations are carried out for the 2-DOF motion of these ships at volume Froude numbers from 0.526 to 5.260. [Results] The calculation results show that resistance and trim angle have almost the same changing trend and it has the relationship in the navigation state of sliding: non step > single step > double steps. [Conclusions] The drag reduction mechanism relates to that the steps change the pressure distribution on the bottom, reduce the wet area and improve the sliding efficiency. The steps make it easier for water-air mixture to enter the steps and gas layer are formed on the surface of glide plane, thus drag reduction is achieved.