Taking Chinese fir sawdust as raw materials, Fe3O4 as the magnetic agent, and hexadecyltrime- thylammonium chloride as well as polyoxyethylene lauryl ether as the surfactant, a successful preparation of magnetic activated carbon has been achieved by adopting vacuum pyrolysis technique. An investigation has been made of the effects of the system pressure, activation temperature, magnetic agent mass fraction and activation time on iodine adsorption value, methylene blue adsorption value as well as magnetic properties of magnetic activated carbon. Test results of the single factor variables show that: the adsorption of iodine and methylene blue on the magnetic activated carbon has shown an initial increasing and then decreasing trend with the increase of pressure, activation temperature and activation time, which shows a decreasing tendency with the increase of mass fraction of magnetic additives. All the factors taken into consideration, the optimum preparation conditions are as follows: its system pressure 10 kPa, its activation temperature 450 DEG C, its magnetic agent mass fraction 10% and its holding time 60 min. Under the optimal conditions, the adsorption value of iodine and methylthionine chloride with magnetic activated carbon will be 935 mg·g-1 and 315 mg·g-1 respectively, while the saturation magnetization of the prepared magnetic activated carbon will be 8.24 emu·g-1，which meets the requirements of recycling activated carbon in medium intensity magnetic fields.