Combination of biomass and coal for energy production is conducive to the sustainable development of society and a clean-energy future. This study investigates co-pyrolysis behavior of raw/torrefied rice straw and coal blends. Mild torrefaction (250 degrees C) and severe torrefaction (300 degrees C) were taken into consideration. Samples of five mixing ratios were tested by thermogravimetric analyzer, and the resulting chars were characterized by Raman spectroscopy and SEM-EDS. The results show that co-pyrolysis had little effect on char yields. Decomposition rate curves showed two distinct peaks for raw/mildtorrefied rice straw and coal blends, and the reaction rate was enhanced below 380 degrees C. However, only one peak appeared for severely torrefied rice straw blended with coal. During co-pyrolysis, the secondary pyrolysis of coal around 700 degrees C was inhibited, and the graphitization degree of biomass char increased, while the crystalline structure of coal char was poorly organized. The activation energy of mixtures also changed in different pyrolysis stages.