The forms of arsenic (As) and lead (Pb) in coal have an important influence on their transformation during combustion. Considering that As and Pb in coal are partially associated with pyrite, pyrolysis and oxidation experiments were conducted on pyrite in a fixed-bed reactor between 600 and 1000 degrees C to study the transformation of As and Pb in pyrite during thermal conversion. During pyrolysis, As remained essentially unreleased below 700 degrees C, and the release ratio increased with increasing temperature above 700 degrees C. At 1000 degrees C, As was almost completely released into the gas phase. During oxidation, As remained essentially unreleased below 800 degrees C, and the release ratio increased with increasing temperature above 800 degrees C, reaching 61.67% at 1000 degrees C. The gas-phase release ratio of As showed a dynamic change that rapidly increased with time, and the change was significantly correlated with the dynamic transformation of the pyrite. During pyrolysis, As was released into the gas phase by a two-step decomposition of FeAs2. In an oxidizing atmosphere, FeAs2 was oxidized to form As2O3 and Fe2O3, which could further react to form FeAsO4. As was retained in the solid phase, and the release ratio of As was therefore lower. During pyrolysis, Pb was released between 600 and 1000 degrees C, and the release rate and release ratio increased with increasing temperature. During oxidation, Pb remained unreleased at 600 degrees C, and the release ratio increased with increasing temperature above 700 degrees C, reaching 87.69% at 1000 degrees C. No significant correlation was found between the release of Pb and the conversion of the pyrite, as Pb exists in the form of PbS in pyrite. During pyrolysis, Pb was released into the gas phase by the decomposition of PbS. Part of the PbS in an oxidizing atmosphere was oxidized into PbO or PbSO4, which remained in the solid phase, resulting in a relatively low release ratio.