Disclosed is a novel double-layer filter material filtration tank applied to oil field sewage treatment. The tank comprises a tank body, a water distribution device, a stirring device, a mechanical sealing device, filter materials and a water collecting device; the water distribution device comprises a filtering water inlet pipe, a water inlet cavity, a water distribution cavity, a water distribution substrate and a water distribution sieve plate; the stirring device comprises a motor, a rotating shaft, a propeller, a shaft sleeve and saw blades; after sewage enters the filtration tank throughthe filtering water inlet pipe, the flow direction of the sewage is distributed by the water distribution device, the sewage is filtered by the multi-layer filter materials, and filtered water is collected by the water collecting device. In the backwashing process, the hardened filter materials can be destroyed by the propeller and the saw blades, and convection flushing of the water and the filter materials is accelerated. The filtration tank mainly solves the problems of incomplete backwashing, instability of the rotating shafts and loss of the filter materials, achieves full automation inthe process, effectively saves manpower, reduces the use cost and improves the work efficiency.