Abstract: In the present study， biochars were fabricated from biomass bamboo， pecan shell， rice and rape straw through slow pyrolysis in a vacuum environment at 300-700 ℃ for 6 h， respectively， and the relationship of material properties， pyrolysis characteristics and biochar yield were investigated by thermal gravimetric analysis. The obtained biochars were characterized in terms of its elemental composition and oxygencontaining functional group composition. It was shown that biomass material compositions had obvious influence on the yield of biochar at the pyrolytic temperature of 300-400 ℃. The biochar yield increased with the increasing of lignin content. Nevertheless， at high temperature （>400 ℃）， the ash content of biochar dominated the biochar yield. Due to the high ash content in the rice and rape straw， the yield of biochar derived from rice and rape straw was higher than that derived from bamboo and pecan shell. With the increasing of carbonization temperature， the ash， ash less carbon content and the stability of biochars increased， except that rice straw still had some oxygencontaining functional groups at high temperature （500-700 ℃）. In conclusion， yield of biochar was dependent on the biomass material at certain temperature， and the stability of biochar was determined by the carbonization temperature in the present study.

Key words: biochar, biomass, carbonization temperature, yield, stability