Abstract: Change of biomass carbonization structure can be characterized by organic element content and functional group． Taking Caragana korshinskii Kom. as experimental object, changes of organic elements in pyrolysis process of biochar were studied by contents of C, H, O, N and S in Caragana korshinskii Kom. biomass raw materials and biochar carbonized at 200, 300, 400, 500 and 600 °C． Effects of pyrolysis temperature on structure of biochar were studied by analyzing composition of functional groups of biochar at different temperatures． Results showed that with increase of carbonization temperature, content of C element increased, contents of H and O decreased significantly, and contents of N and S elements remained basically unchanged． Both H/C and O/C molar ratios decreased． Changing of functional groups of biomass with increasing of temperature indicated biochar gradually changed from linear polysaccharide to thick cyclic aromatic hydrocarbon structure, and finally formed a structure similar to graphene．