Infrared spectroscopy (IR) is an important means of seeing the characteristics of the structural properties. Fourier transform infrared spectroscopy (FTIR ) was applied to analyze the structural properties of biochar from different materials with different methods. The results showed that: the biochars have IR absorption peaks of hydroxyls group, aromatic group and containing organic group with the activated?charcoal, but in other absorption peaks, with a significant difference. The high temperature can make —OH, —CH3, —CH2—, CO to be associated or loss, and promotes the formation of aromatic groups during Carbonization of corn straw. At the different carbonization mode, the heating and microwave carbonization, has a carbonize mechanism of biochar, heating method may make —OH in alcohol and phenol to combinative with each other or loss, and to form benzene ring group and an aromatic group, Aromatic group in microwave method was so preventing to participate in the hot reaction, to form the more benzene substances. These results show that the Infrared spectrum can well analysis the structural characteristics of biochar, and showed that it comprises —OH, the aromatic group and other active groups.