The contents of oil, polymers, solid particles, inorganic ions and bacteria in water with or without pretreatment were analyzed respectively by means of various chemical and physical methods, which was produced from formation with PAM flooding in Nanshan Area, Daqing oilfield. The diameters and their distribution of solids were also measured by laser granularity equipment. According to the chemical and physical properties of these materials and their damage mechanism to oil formation, the damage contents were determined. The sulphate-deoxidized bacteria are main damage contents for the rejecting of water into formation. Solid particles and oil can damage formation with medium or low permeability, and PAM can damage formation with low permeability. The usual pretreatment of water can remove oil significantly, but have some effects for removing PAM and particles.