The invention provides a calculation method for predicting the ship resistance based on CFD, and the method comprises the steps: S1, employing a two-phase incompressible RANS as a control equation, which comprises a continuity equation and a momentum equation; S2, processing a free surface through employing a single-phase level set method; S3, enabling a computational domain to be discretized into a series of small units through employing a finite volume method, calculating flow field information, and storing the flow field information at the gravity center of a grid unit; S4, obtaining values of unit surfaces according to the interpolation of the gravity center of the units; S5, solving the sum of the values of the unit surfaces, and obtaining the volume integral of a unit body; S6, carrying out the iterative solving of a pressure speed coupling equation, obtained after discretization, through employing a PISO implicit separation algorithm, wherein the calculation of each time step comprises momentum estimation, pressure solving and speed correction; and finally obtaining a convergent numerical solution. The method employs CFD to calculate and obtain a total resistance coefficient of a ship at a certain operating speed, and calculates and obtains the total resistance of the ship through a simple formula. The method is high in efficiency, is accurate, and is very strong in engineering practicality.