Abstract: In this paper, a four-propeller surface ship is studied and an integral mathematic model including the hull appendage and propellers is established. Using a RANS solver and moving grids， the self-propulsion factors are predicted by gradually modifying the rotation speed of the propeller and by respectively calculating the propeller features. The result shows that the self-propulsion factors of the inner propeller differs from those of the outer propeller. The wake fraction and thrust deduction fraction of the inner propeller is bigger than the outer propeller's. In brief, the differences among four-propeller ship self-propulsion factors can be observed and are seen to fit the ordinary relation of thrust deduction and wake, which validates the reliability of the new proposed method and provides the basis for future self-propulsion tests of multi-propeller ships.