The production of tunable syngas from biomass will further establish the role of biomass-derived syngas as a versatile platform for liquid fuels and value-added chemical synthesis. This study introduced steam, Ni–CaO catalyst, and biochar into a proposed two-stage sorption-enhanced catalytical thermochemical conversion process, aiming to obtain the tunable syngas through the in-situ stepwise generation of high purity H2 and CO. The presence of steam and Ni–CaO catalyst shows unprecedented performance in enhancing the H2 generation due to the promotional tar steam reforming/cracking and water-gas shift reactions at the first stage, and the control experiments indicate that the steam performs a higher selectivity to H2 than the Ni–CaO catalyst. The introduction of biochar with a supplementary carbon source, remarkably promotes the CO generation at the second stage, which could be further pronounced by the addition of Ni–CaO catalyst. A synergistic effect of steam, Ni–CaO catalyst, and biochar contributes to a significant enhancement in H2 and CO generation with an inherently separated generation of H2 (88.2 ± 2.3 vol% of purity) and CO (55.6 ± 1.3 vol% of purity). And the combined use of steam, Ni–CaO catalyst, and biochar could lead to a superior syngas quality with high LHVsyngas and energy recovery efficiency.