To investigate the effect of airway parameters on the temperature rise characteristics of large dry-type transformer core, a calculation model of natural convection in a finite space environment is established for a large core structure. Numerical simulations on the temperature rise of the core are conducted with 8 mm ~ 25 mm in the widths and three different materials of the airways. The results show that the overall temperature distribution of the transformer core follows that the temperature increases along the height, at the same time the temperatures of the middle and interior of the core are higher than those of the side and outside, which are consistent with the actual conditions. Based on the analysis of Ra# and the velocity distribution inside the airway, the height of the hot spot moves from 66% to 80% of the total height as the airway width increases, meanwhile, the temperature of the hot spot decreases exponentially with a high fitting relationship equation. Finally, increasing the thermal conductivity of the air ventilating ducts can effectively reduce temperature of hot spot of the core, but it has little influence on the velocity distribution inside the airway. This study provides reference for selecting appropriate parameters of the airway in the design process of the core.