Abstract: This paper addresses three major technical challenges in the industrial application of oil shale pyrolysis: accelerated equipment corrosion induced by sulfur compounds, aggravated exhaust emissions, and quality deterioration of pyrolysis products. A coupled regulatory system integrating “atmosphere-sulfur speciation” is established to systematically investigate the migration behavior and chemical transformation pathways of sulfur during pyrolysis and gasification. The synergistic regulation mechanisms of multi-reaction atmospheres on sulfur speciation evolution are thoroughly explored, aiming to provide theoretical and technical foundations for developing clean pyrolysis processes with targeted sulfur conversion. Programmed temperature pyrolysis experiments are conducted on oil shale samples with a carbon content of 46.47% and an iron sulfide content of 9.74%. The research framework encompasses two dimensions: reactive atmosphere regulation and sulfur speciation evolution. Fourier transform infrared spectroscopy （FT-IR） and X-ray diffraction （XRD） are employed to characterize sulfur transformation pathways under varied atmospheres. Experimental results demonstrate that FeS content decreases to 1.10% in H₂/CO₂ mixed atmosphere, while further reduction to 0.80% （91.8% decrease from raw material） is achieved in ternary H₂/CO₂/H₂O atmosphere. Mechanistic investigations reveal that inert atmosphere primarily facilitates H₂S release from pyrite and aliphatic sulfur; H₂ atmosphere promotes cleavage of organic macromolecules; CO₂ enhances organic matter gasification; whereas the reactive hydrogen atoms generated by the water-gas reaction of H₂O steam remove FeS effectively. This work innovatively elucidates the targeted transformation patterns of sulfur speciation under multi-atmosphere synergy, confirming that mixed atmospheres enable deep desulfurization. It establishes a theoretical foundation for developing green semi-coke preparation processes with low sulfur content, providing crucial engineering guidance for advancing efficient and clean utilization of oil shale resources.