Firstly the author considered, for the sake of simplicity, the case of a prolate spheroid and a sink propeller abaft, both advancing in a same direction of axis at fixed immersion under the free surface, and then he obtained theoretically the change of flow around the spheroid due to the suction of the propeller, which had been unduly neglected as small in the former theory of mutual interference, in the form of power series distributions of source and sink. Then he calculated the resistance augmentation by the theory of wave resistance, and finally, discussed some interesting conclusions coming from the numerical results obtained.