Magnetic biochar-based composites were prepared by the methods of impregnation, chemical precipitation and anoxic pyrolysis using wheat straw and poplar sawdust as raw materials respectively. The effects of loading iron were studied at different pyrolysis temperatures based on the physiochemical characteristics. The results showed that the iron in the composites mainly existed in the forms of Fe3O4, and the outer layer content was higher than that in the inner layer. The loadingiron treatment accelerated the dehydrogenation and deoxygenation processes during biomass pyrolysis, and the influence tended to augment with increasing temperature. At the temperature of 300~600℃, the contents of ash in the biochar derived from wheat straw and sawdust was increased by loading iron within the ranges of 28.8~34.4 percentage points and 39.1~47.6 percentage points, respectively. Both of the fixedcarbon content and calorific value were reduced. The specific surface area and total pore volume were increased by loading iron within ranges of 10.67~72.24m2/g, 0.0398~0.0931cm3/g and 15.43~10514m2/g, 0.0104~0.0789cm3/g, respectively. The average pore size was decreased. Different effects on the content of volatile matter of the wheat straw and sawdust derived biochars were indicated as well as on the pH values. The volatile content of wheat straw derived magnetic biochar was increased by 5.2~13.2 percentage points, while for the sawdust, the volatile content was reduced by 174 percentage points at 300℃, and then increased by 8.5~22.2 percentage points during 400~600℃. The pH value was decreased by 0.04~1.49 for the former but increased by 0.33~1.93 for the latter.