Abstract: Reservoir stemming in polymer-injection wells in SZ36-1oil field was analyzed by applying x-ray polycrystalline diffraction, scanning electron microscopy/spectroscopy, infrared spectroscopy and so on, and the stemming formation mechanism and its micro morphology were studied. The results show that the most common blockage is soft-hard combination complex scale, and the main mechanism is: under the formation conditions in SZ36-1 oil field with clearly scaling tendency, the high molecular polymer adsorb and wind around a core of inorganic to form complex scale winded by the colloidal organic and inorganic matters; and following, the polymer molecules cross-link in response to the high valence metal ions in the formation to form lumpy reservoir stemming; besides, the hydrophobic associating polymers in the porous media form the super molecule polymer structure by association reaction, increasing the viscosity, establishing a high flow resistance and reducing the reservoir permeability.