In order to study the influence of built-in fin parameters on the heat transfer of turbulent natural convection in the enclosed cavity, the RNG k-ε model was used to numerically analyze the comprehensive effects of the fin position, the fin height and the fin number on the temperature and flow field. When single fin is arranged on the hot wall, the thickness of the vertical boundary layer close to the hot wall becomes thicker with the increase of the fin height, but the structure of the horizontal boundary layer close to the top of the cavity changes slightly. The height of the short fin studied in this paper has little effect on the local heat transfer characteristics at the location away from the fin on the hot wall. The average Nu number on the hot wall can reach the maximum value when the fin with the height of 1.5 cm is arranged at 2H/6 from the bottom of the hot wall, and the same average Nu number on the hot wall can be achieved by placing one fin with the height of 1.5 cm on the hot wall at 2H/6 from the bottom and the other on the cold wall at 2H/6 from the top of the cavity. When a fin is arranged on the hot wall at H/6 from the bottom and the other on the cold wall at H/6 from the top of the cavity, the convective heat transfer efficiency between the hot wall and the air flow in the cavity will be restrained if the fin height is too high or too low. The results of this paper have a certain theoretical reference value to guide the cooling or heating of fluid in enclosed space in industry engineering.