NH₃ and HCN are the main nitrogen containing compound in the pyrolysis process and important NO_x precursors in the combustion process of solid fuel. The conversion and control rules of HCN and NH₃ during the pyrolysis process are of great significance to reduce the NO_x emission. Experiments using the TG-MS technique were carried out to analyze the release behaviors of NO_x precursors in the pyrolysis process of Zhun Dong high-iron content coal and straw stalk. The results indicate that the NH₃ is the main NO_x precursors product in the pyrolysis process of Zhun Dong high-iron content coal and straw stalk. The release behaviors of NH₃ with HNCO and HCN with CH₃CN are similar. The emission of NO_x precursors in the straw stalk pyrolysis process is apparently more than in that of Zhun Dong high-iron content coal. The experiments show that iron compounds and minerals in coal have reduction effects on the NO_x precursors release. In co-pyrolysis process of Zhun Dong high-iron content coal and straw stalk, with the mass percent of straw stalk increased from 10% to 40%, the emission of NO_x precursors is firstly reduced then increased. The emission is the lowest at the mass percent of 30%. It is shown there is synergistic effect on the reduction of NO_x precursors release by the co-pyrolysis of Zhun Dong high-iron content coal and straw stalk.