<p>This study investigates the impact of fin parameters on natural convection heat transfer in the closed cavity with a heat source. The analysis focuses on the comparison of the thermal performance between solid and porous fins. Firstly, the influence of individual parameter changes is analyzed. Based on these findings, the response surface optimization method is applied to explore the heat transfer characteristics when multiple fin parameters vary simultaneously. The results of single parameter variation show that the installation angle of porous fins has the most significant influence on the average <i>Nusselt</i> number of the heat source surface. For solid fins, the fin length has the greatest impact. The interaction between the installation angle and the length of the porous fin has the most significant effect on the average <i>Nusselt</i> number of the heat source surface, reaching a maximum value of 11.65. Compared to the cavity without fins, the optimal configuration enhances the average <i>Nusselt</i> number by 12.02%. The corresponding optimal parameters for the porous fin are <i>θ</i> = 118.3°, <i>l</i> = 0.288<i>H</i> and <i>a</i> = 0.664<i>H</i>. Similarly, for the solid fin, the interaction between the installation angle and fin length has the most significant effect on the average <i>Nusselt</i> number of the heat source surface. Correspondingly, the maximum average <i>Nusselt</i> number on the surface of the heat source reaches 11.57, representing an 11.32% increase compared to the cavity without fins. The optimal parameters for the solid fin are <i>θ</i> = 108.9°, <i>l</i> = 0.021<i>H</i>, <i>a</i> = 0.747<i>H</i>.</p>