Biomass pyrolysis experiments were performed in a tubular reactor at different temperatures, the effects of which on organic structure of semi-char and tar had been investigated. Fourier-transform infrared (FTIR) analysis was conducted by a Nicolet 6700 FTIR spectrometer. The tar components at different temperatures were analyzed by GC/MS. It was observed that pyrolysis of biomass mainly occurs in the temperature range of 300-600 degrees C. A high temperature favored the production of gases. The yield of semi-char and the contained organic functional groups(C=O, C=C, C-H, C-O and OH) decreases significantly with the increasing final temperature. The tar yield passes through a maximum at about 500 C. The organic functional groups in tar were stable but the transmittance of these groups decreased with the increasing final temperature. (C) 2012 Elsevier Ltd. All rights reserved.