Abstract: Aiming at the problem of high carbon emission from carbonate pyrolysis under the “dual-carbon” strategy, Mn-doped modified NiMnAl catalysts were developed in this study. The NiMnAl catalysts prepared by sol-gel method showed significant performance enhancement at 750 ℃: The CH₄ conversion increased from 11% to 16% with NiAl, the H₂/CO tended to be close to 1, and the amount of carbon deposits decreased by more than 20%. Characterization analysis showed that Mn doping enhanced the lattice oxygen mobility through electronic structure rearrangement and in-situ formation of MnO₂ active phase, increased the specific surface area from 63.215 m²/g to 82.087 m²/g, and optimized the pore structure. The synergistic mechanism resulted in a combination of high activity and anti-carbon deposition: thermogravimetric analysis showed that the onset oxidation temperature of carbon deposition was reduced, and the amount of carbon deposition was further reduced when a small amount of O₂ was passed through the catalyst, and XRD and BET showed that the pore structure damage caused by the carbon deposition could be effectively mitigated by the oxygen-ventilated condition. This study provides a theoretical basis for the development and industrial application of highly efficient anti-carbon deposits catalysts.