We conducted a comprehensive investigation into the mechanisms the enhancement of pool boiling heat transfer. Created a porous medium composite free particle reinforced structure (FPPM). FPPM is synthesized with copper foam (Cu foam) with a porous structure as the base material; it is characterized by free particles inside the cavity. We used deionized water (DI water) as the working fluid to study the heat transfer performance of pool boiling on different surfaces under atmospheric pressure. The boiling mechanism was verified by bubble dynamics. The findings showed that the addition of free particles to the copper foam sample significantly reduced the superheating of its onset of nucleate boiling (ONB). Compared to the polished surface, a maximum of 2.57 times the heat transfer coefficient was achieved; in addition, a maximum of 1.59 times the heat transfer coefficient was achieved compared to the copper foam surface without free particles. The visualization results showed the formation of nucleation sites on the surface with free particles, which decreased the energy barrier to easy nucleation. During the boiling process of the pool, the high thermal conductivity of free particles and the disturbance to the gas–liquid layer significantly reduced the bubble detachment frequency, resulting in good heat transfer performance over the whole range of heat fluxes.