In order to understand the laws of HPAM adsorption and desorption，the dual polarization interferometry （DPI） technology was introduced to study the microcosmic adsorption and desorption behavior of polymer in the oil-water interface，the thermodynamic and kinetic model for polymer adsorption was established，and then the mechanism of the polymer adsorption in oil-water interface could be revealed from molecular level，providing new ideas and theoretical basis in the treatment of polymer-contained water. It was demonstrated that polymer displayed fast adsorption-slow desorption process in the oil-water interface. The maximum adsorption showed a linear relationship with the polymer concentration. The polymer adsorption capacity was significantly affected by the polymer molecular weight，hydrolysis degree and hydrophobic monomer content. Absorption kinetic parameters conformed to the pseudo-first order kinetic rule. Under different concentration，the corresponding reaction rate constant K was 0.029 s^-1. After long time desorption，there were still residual polymer in the oil-water interface. The residual quantity increased with the increase of polymer concentration.