The underwater fan-wing thruster (UFT), which is composed of a fixed wing and a cross-flow fan (CFF) under the fixed wing, has excellent underwater propulsion performance, especially for vertical propulsion. Despite prior experiments and simulations in analyzing the UFT, the effects of the CFF on the performance of the UFT have not been studied in depth. In this paper, the hydrodynamic and acoustic performance of UFT is studied by computational fluid dynamics (CFD) simulations with different CFF parameters, including the number of blades, internal to external diameter ratio, internal blade angles, and external blade angles. Towing experiments are also carried out for verification. Based on cloud and vector maps generated by CFD, the effect mechanisms of parameter variation are also analyzed. The effects of CFF on the UFT are finally summarized, and the best sets of parameters are discussed based on the real working conditions of UFTs.