The utility model discloses a system for biological carbon composites of preparation magnetism, include: pyrolysis activation device, breaker, load device and back processing unit. Wherein, have the radiant tube in the pyrolysis activation device, pyrolysis activation device has biomass feedstock entry, water vapor inlet, high -temperature oil -gas well export and the export of active biological charcoal, breaker has active biological charcoal entry and the export of active biological carbon powder, and active biological charcoal entry links to each other with the export of the biological charcoal of activity, the load device has active biological carbon powder entry, mixes molysite solution entry, alkali lye entry and result export, and active biological carbon powder entry links to eachother with the export of the biological carbon powder of activity, back processing unit links to each other with the result export of load device including the filter equipment, belt cleaning device and the drying device that link to each other, filter equipment, and drying device has the biological carbon composites export of magnetism. The magnetism biology carbon composites who adopts this department to control fully has better stability, magnetism and stronger adsorption efficiency.