Abstract: To address the critical challenges in traditional Wacker oxidation, such as the difficult separation of homogeneous catalysts, heavy metal pollution, and oxidant toxicity, a green catalytic system based on a coal-based humic acid (HA)-supported Pd catalyst (Pd/HA) is designed and constructed. Hydrogen peroxide (H₂O₂) is used as an alternative to the conventional copper salt/oxygen oxidation system. Coal-based HA is extracted by an optimized alkali dissolution-acid precipitation method, and excellent aqueous dispersibility and support functionality are achieved. The Pd/HA catalyst is prepared by an impregnation method. It is confirmed by TEM and XPS that palladium species are uniformly anchored in the three-dimensional porous structure of HA as nanoparticles with a size of 2–5 nm, forming stable coordination with carboxyl and phenolic hydroxyl groups on the support, thereby effectively inhibiting metal leaching. The optimal reaction conditions (45 ℃, 13.5 min, and 3.16% Pd mass ratio to styrene) are obtained by response surface methodology. A conversion of 91.5% and a selectivity of 96.9% are predicted by the model. Under the validation conditions (45 ℃, 13.5 min, and 3.16% Pd concentration), a conversion of 92.6% and a selectivity of 94.9% are obtained, which are in good agreement with the predicted values. After five cycles, a conversion above 90% is maintained, and the palladium leaching rate is below 2.6%, indicating excellent recycling stability and reusability. Moreover, good versatility of the Pd/HA catalyst is observed in classic palladium-catalyzed systems, such as the Suzuki coupling reaction and the Heck reaction, confirming its potential as a universal heterogeneous catalyst. A high-value utilization route for coal-based humic acid as a high-performance catalyst support is provided, and a low-cost, highly stable green catalytic system is established, with both environmental and economic benefits and promising application prospects in fine chemical synthesis.