To study the effect of volatile-char interaction on biochar functional groups, the one-stage fluidized bed/fixed bed reactor and Py were used in the experiment, and the biochar structure was analyzed by Fourier transform infrared spectrometer in the qualitative and semi-quantitative aspects. The results show that with the increase of temperature, the influence of interaction on biochar structure is more intense. The characteristic peaks of biochar functional groups are reduced and the species of peaks are reduced due to the volatile-char interaction which has a destructive effect on the alkyl side chain and accelerates its detachment from aromatic ring. Without the volatile-char interaction or with the interaction but at low temperature, the maturity of organic matter of biochar increases with the increasing of temperature. However at high temperature, the parameters decrease and the free radicals generated by the volatile splitting can cause the condensation of aromatic ring, which leads to the increase of C_ar content.