Dynamic simulation experiments were operated so as to evaluate the recovery efficiency of the two types of simultaneous water and gas injection（SWAG）systems：the nitrogen-water system and the nitrogen-active water system. Their enhanced oil recovery mechanism and permeability adaptability were probed as well. The result suggests that the mobility reduction factor（MRF）of the nitrogen-water system reduces as permeability rises when it ranges from 5×10-3 to 100×10-3 μm2. The nitrogen-water system can enlarge swept volume and improve recovery efficiency by 35.1%-16.8% after water flooding in the scope of 5×10-3 to 40×10-3 μm2. MRF can be used as a criterion to evaluate the sweep efficiency enlarging ability of SWAG for it matches well with recovery degree. When permeability ranges from 30×10-3 to 500×10-3 μm2，the nitrogen-active water system can improve percolation resistance effectively and enhance recovery degree by 22.6%-19.4% after water flooding. Therefore，the nitrogen-water system can be adapted to the formation with permeability under 40×10-3 μm2，whereas the nitrogen-active water system may be applied to the formation with the permeability between 30×10-3 and 500×10-3 μm2.