Abstract: Using wheat straw as the main raw material and KOH solution with 10% mass fraction as the impregnating agent, biomass carbon was prepared by controlled thermal decomposition at 350℃ and 410℃, respectively. The properties and structures of raw materials and biochar were characterized by thermogravimetric analysis, infrared spectroscopy, Raman spectroscopy and X-ray diffraction. The results showed that the maximum weight loss rate of wheat straw was 72%, and the thermal weight loss rate reached the maximum at 335℃. The types of functional groups of the biochar prepared at two temperatures are basically the same, and the degree of aromatization and graphitization of the biochar prepared at higher temperatures is higher, which is beneficial to enhance the chemical stability of the biochar.