Abstract: The damage mechanism of water-injection wells in Bonan Oilfield is studied systematically in this paper. We drew some conclusions, according to analyzing and experimenting on the potential damage of formation characteristics(clay mineral, low-porosity and low-permeability), the potential damage of defective acidizing treatment and re-acidizing treatment, the potential damage of formation fluids, the formation sensitivity damage and reservoir protection, the damage of low-permeability formation of pre-stimulation treatment. The results supply theory basis for acidizing treatment of water-injection wells in Bonan Oilfield.