The physical and chemical properties of biochar are mainly determined by matrix materials and pyrolysis conditions. Taking the corn cob, soybean stalk, and rice husk as test materials, and by using muffle furnace, this paper studied the effects of pyrolysis temperature (300, 400, 450, 500, and 550 ℃) and pyrolysis duration (3, 6, and 9 hours) on the biochar yield, its pH, and carbon and nitrogen contents. With the increase of pyrolysis temperature and duration, the biochar yield decreased, while the biochar pH increased. The carbon content of the biochar produced from corn cob and soybean stalk increased with the increase of pyrolysis temperature and duration, while that of the biochar produced from rice husk had less change. The nitrogen content of the biochar produced from soybean stalk decreased with the increase of pyrolysis temperature and duration, while that of the biochar produced from corn cob and rice husk had no regular change.