Abstract: Establish the test method of the separation and concentration, molecular weight and degree of hydrolysis of micro-polymer in core of sealing core well, studied the performance alternation of residual polymer in formation, and analyzed the law of adsorption and retention of polymer in flat, intra-formation and interlamination of oil layer after polymer flooding, and studied the relation of polymer's adsorption-retention amount and remaining oil saturation, as well as the structure and form of the residual polymer in oil layer by infrared spectrum and SEM. It is found that the performance of polymer has changed greatly after polymer flooding, the degree of hydrolysis has increased to 50% or so, the molecular weight has reduced to about 1/10 of original injected HPAM; but the main composition is still HPAM, it exists in the oil layer by the form of flocculated aggregate; the adsorption and retention of polymer is common in flat after polymer flooding, and the amount of absorption and retention is low in residual oil abundance zone.