The invention aims to provide a method for improving oil removing efficiency of oil removing bacteria. According to the microorganism oil removing method, a magnetic field is additionally arranged around the oil removing bacteria, in the mode of adjusting the intensity and action of the magnetic field, the degrading effect on petroleum and the capacity for resisting impact loads of the oil removing bacteria can be effectively improved, process operation stability is improved, and the method belongs to the field of biological treatment on oily sewage. An adopted permanent magnet is a round ferrite permanent magnet, according to the action condition, the magnetic field intensity is 18-35 mT, and the magnetic action is continuous. The magnetic field is generated by the commercially available permanent magnet, the needed magnetic field intensity is low, electric energy consumption is not needed, investment is low, the effect is good, an existing process flow path is not changed, arrangement of large equipment is avoided, and the enhanced oily sewage treatment technology is suitable for the situation of China, economical and feasible.