With the increasing load of the nuclear power plant, the requirements for the performance of steam-water separators in steam generators are increasing daily. In order to optimize the design of the wave type separator in AP1000, this paper uses FLUENT to establish the 2D and 3D models. Numerical calculation and analysis are carried out in hot conditions by changing the structural parameters, such as plate spacing, plate-hook distance, and hook length. These parameters' influence on wave type separator characteristics are obtained, then seven optimization schemes are established for calculation. Finally, verified by 3D calculation, three optimization schemes are determined. The main results are as follows: Compared 2D calculation with 3D calculation, in hot conditions, the pressure drop calculated in the 2D model is higher, and the calculation accuracy of velocity is a little poor. As for the structural parameters, with the increase of plate spacing, the pressure drop and separation efficiency decrease generally, and a local minimum pressure drop exists in part of the range. The pressure drop and separation efficiency increase with the increase of plate-hook distance or overall hook length. For the final optimization schemes, through 3D verification, plate IV-Y has the best all-around performance among the seven schemes, which can improve efficiency and reduce pressure loss simultaneously. When pressure loss is out of consideration, plate V–P has the best optimization performance on separation efficiency. When considering the manufacturing difficulty, the basic optimization plate will be an appropriate choice, also obviously improved the efficiency. The research results provide support for miniaturization design of steam-water separators in reactor.