Abstract: The straw pyrolysis chars obtained at 873, 1 073 and 1 273 K were investigated with SEM, BET and TGA to conduct the characterization. The reduction of NO by different straw chars was investigated, with considering the effects of char concentration c_char and NO concentration c_NO, to analyze the effect of pyrolysis temperature on the chemical physical characteristics of biomass char. The results show that straw char obtained at 1 073 K holds the most developed pore structure and surface area, the best combustion activity, and the highest NO reduction rate. As the char concentration increases, NO reduction rate linearly increases. As the NO concentration increases, NO reduction rate decreases as a power-function relation. At the transition temperature about 1 173 K the char-NO reaction changes from dynamic-control region to diffusion-control region. In the dynamic-control region, the pyrolysis temperature affects the activation of the char-NO reaction inconspicuously. The reaction orders for NO and straw char are found to be 0.89 and 1.00, respectively.