Phase change materials (PCMs) are crucial for thermal management systems but are limited by their low thermal conductivity and poor heat transfer properties. To address these limitations, a novel cascade enhancement structure for PCMs was proposed. In the design, PCMs with progressively lower melting points are arranged along the heat transfer direction, allowing active control over the solid-liquid interface during the melting process. The arrangement enables the synchronous melting of multi-stage PCMs, significantly enhancing heat transfer efficiency without requiring additional materials. The heat transfer characteristics of the cascade PCM heat sinks were investigated using both experimental and numerical methods. The effect of heat flux on the effectiveness of the cascade structure was analyzed. Results show that the cascade structure significantly improves thermal management compared to traditional single PCM setups, achieving a maximum enhancement of 25.48% in heat transfer. Additionally, the numerical investigation of the PCM stage arrangement revealed that a three-stage setup is optimal for cascade PCM heat sinks. Specifically, arranging the heights of the three-stage PCMs to increase along the heat transfer direction is recommended. The cascade enhancement structure not only surpasses the maximum heat flux constraints typical of conventional single PCM setups but also extends the effective duration of thermal management, providing a powerful solution for enhancing the heat transfer capabilities of PCMs.