Wood powder is cheap and has a wide range of sources. It contains a large amount of lignocellulose，which is biodegradable and environmentally friendly. The oil-displacement agent compositing wood powder and hydrogel can effectively reduce the cost of production. This work used acrylamide（AM）as monomer，poplar wood fiber mechanochemically modified by ball milling（PWF-BA）as filler，potassium persulfate（KPS）as initiator，N，N'-methylenebisacrylamide（MBA）as crosslinking agent，to synthesize wood powder composite hydrogel. The elasticity，viscosity，shear resistance and anti-aging property of the composite hydrogel under high temperature and high salt conditions were studied. The results showed that after chemical treatment， the lignin and hemicellulose in the wood powder were basically removed. As the milling time increased，the particle size and crystallinity decreased significantly，and the specific surface area increased. When the ball milling time was 4 h，the wood powder obtained had good dispersibility and interfacial interaction in the polyacrylamide matrix. The tensile property of the composite hydrogel and the anti-aging performance in salt water at 85 ℃ were good. The hydrogel was expected to be used as an oil displacing agent in tertiary recovery.