Abstract: Using numerical simulation methods, the thermodynamic and hydraulic parameters in the fuel bundle channel, especially downstream of the positioning grid, were calculated under different Reynolds number conditions. The effects of different punching models on the velocity and turbulence intensity in the downstream of the positioning grid were analyzed from the aspects of pressure drop, Nusselt number and comprehensive local heat transfer factor, and the optimal punching area within different Reynolds number ranges was calculated. Results show that when the Reynolds number is not less than 5 871, compared with the unperforated model, the perforated model can effectively reduce the pressure drop in the downstream section. When the Reynolds number is greater than 6 605, punching holes on the surface of the turbulent blade can reduce the longitudinal vorticity at the blade outlet, which leads to a decrease in the Nusselt number in the far field of the downstream flow field. When the Reynolds number is less than 7 339, the comprehensive heat transfer factor increases the most when the punching area ratio is 15%. However, when the Reynolds number is greater than 7 339, the local comprehensive heat transfer coefficient in the downstream far-field will gradually decrease with the increase of punching area.