Taken a catamaran as the research object, based on STAR-CCM＋ simulation software, according to the requirements of grid independence verification and time step independence verification, the static water resistance of the catamaran is verified with the numerical method, and the accuracy of numerical calculation results is proved. The numerical calculation of operation conditions such as different demihull spacing, different demihull forms, and different oblique sailing angles is made, and the hydrodynamic performance of the catamaran is analyzed. The calculation results show that: when the catamaran is in the direct sailing, under the operation condition with demihull spacing ratio of 0.2 and Froude number of 0.4, the static water resistance is of an obvious sudden rise compared with other operation conditions with the same speed, and the total resistance coefficient reaches the maximum value of 14.56×10-3; when the demihull is rotated outside by 2°, the resistance value is minimal compared to other rotation angles. It is found that, no matter in case of direct sailing or oblique sailing, the total resistance coefficient of the catamaran presents a trend of first increasing and then decreasing, which shows that the catamaran is of certain superiority when it is in high-speed sailing.