Pyrolysis of maize stalk and rice straw was studied using a thermogravimetric(TG)analyzer and a laboratory scale fixed bed coupled with Fourier transform infrared spectroscopy(FTIR).The char structural evolution properties during biomass pyrolysis were also investigated by diffuse reflectance infrared Fourier transform spectroscopy(DRIFT).Pyrolysis characteristics of the two materials were discussed.Maize stalk showed the higher thermal reactivity than rice straw.Their pyrolysis processes underwent three consecutive stages,corresponding to the evaporation of water,the formation of primary volatiles and the subsequent release of small molecular gases.The interpretation of the FTIR spectra showed that the major pyrolysis gases for the two materials were similar,including CO2,CO,methane,ethane,and some organics such as methanol,formaldehyde,formic acid,acetic acid and acetone.The release of CO2 and CO was mainly caused by the cracking and reforming of carbonyl,carboxyl and ether groups.CH4 evolution was mainly due to the cracking of methoxyl groups.Moreover,the rupture of methylene groups could also generate CH4.The DRIFT analysis showed that the hydroxyl,aliphatic C–H,carbonyl and olefinic C=C functional groups were lost at high temperatures.The aromatization process started at ≈ 400 ℃ and continued to higher temperatures.