Paraffin is a low-temperature phase change material, which is often used to recover and store heat in a solar thermal utilization system. This study aims to reveal the development and migration law of paraffin melting interface with time under the influence of a finned heating plate, as well as the heat transfer mechanism, and obtain the ways and methods to enhance the heat transfer in phase change material through visual experiments and numerical simulation. The research shows that once the paraffin with a high liquid fraction connects the mushy zone between the fin and the top wall, the vortexes in the mushy zone increases rapidly, which enhances the natural convective heat transfer in it, resulting in the rapid increase of liquid fraction. The lower the position of the fin, the longer the time required to form a mushy zone with a high liquid fraction between the fin and the top wall, and the later the phenomenon of rapid increase of liquid fraction occurs. Compared with changing the fin position, increasing the fin length has a greater effect on the paraffin melting rate. When other conditions remain unchanged, the inclination of fin and the effective length of fin in the horizontal direction jointly determine the melting rate of paraffin. The melting effect of paraffin is the best when the fin is inclined upward by 15°.