Well casing damage is a commonly existing problem in oilfield exploitation in the world. Daqing oilfield is a multiple-zone, heterogeneity sandstone oilfield, where the major influence factors which lead to casing damage are geologic factor, engineering factor, high pressure water injection and chemical factors. Among them, the high pressure water injection is the most important one. Water injection exploitation in Daqing oilfield showed that casing-damage increased with the increasing water injection pressure. However, the mechanism is not totally understood and the control method is not well developed yet. In the present work, the mechanism analysis of casing damage induced by high pressure water injection in Daqing oilfield is proposed. It is found that after high pressure water injection, the sandstone layer will expand and result in the vertical elongation of the casing. The additive tensile stress of the casing induced by vertical strains will cause casing-damage. Besides, the horizontal deformation of clay-stone increases with increasing water content of the formation layers and soaking time. The cohesion of clay-stone and inner friction angle decreased with increasing water quantity. In that case, some high obliquity formation layers which may induce high hypsography pressure difference will cause localized slip along weak formation layer interface in the area of waterishlogged clay-stone. Casing damage and well failure caused by the relative movement of the formation layer interface may therefore occur. The micro-fracture of formation induced by high pressure water injection also educed formation rupture and casing damage.