With the increasing environmental problems such as depletion of fossil energy and global warming, marine renewable energy (offshore wind energy, tidal energy and wave energy) has become a research hotspot. In order to effectively develop marine renewable energy and reduce costs, comprehensive development of multiple energy sources has become a trend at this stage. The combination of offshore wind energy and wave energy has broad application prospects, and the combined power generation system continues to innovate. Hydrodynamic performance is an important basis for the interaction of combined system with waves. This paper introduces briefly a variety of hydrodynamic numerical simulation methods for combined power generation systems, including linear frequency domain, linear time domain, potential flow nonlinear method, and viscous method based on Navier-Stokes equation. The numerical simulation method is reviewed, and its advantages and disadvantages are analyzed from the aspects of computational efficiency and precision. The technical principle and main research difficulties of hydrodynamic control optimization and experiments are further elaborated, which provides a basis for the hydrodynamic design of the combined power generation system. The main conclusions are as follows. Firstly, from the perspective of computational efficiency, the linear frequency domain method is optimal, followed by linear time domain, potential flow nonlinearity, and viscous method. From the perspective of computational accuracy, it is the opposite of the former. Secondly, considering the computational efficiency and precision, it is a feasible solution to study the potential flow theory considering viscosity correction. Thirdly, at present, model experiment method and optimal control technology are not mature and still in the exploratory stage.