Abstract: The mutual interaction between the cationic monomer methacryloxyethyl trimethyl ammonium chloride(DAC) and bovine serum albumin(BSA) were first examined by UV absorption spectrum and fluorescence emission spectrum. The grafted particles SiO2-g-PDAC were prepared using a surface initiated graft polymerization technique, and the mutual interaction between the grafted macromolecule PDAC and BSA was also investigated in depth. Results show that in aqueous solutions, there is a strong electrostatic interaction between the cationic monomer DAC and BSA. By right of this strong secondary bond force, a host-guest complex of DAC and BSA can be formed, and the stronger electrostatic interaction between monomer DAC and BSA exists in neutral solutions. There also exists a strong electrostatic interaction between the grafted macromolecule PDAC and BSA, and so the grafted particles SiO2-g-PDAC can produce strong adsorption action for BSA. The pH value and the temperature of the medium affect the adsorption property of the grafted particles SiO2-g-PDAC for BSA greatly. The adsorption capacity for BSA is the greatest as the pH value of the medium is nearby the isoelectric point of BSA (4.7). Raising temperature is disadvantageous to the electrostatic interaction between host guest, and so the adsorption capacity of BSA on the grafted particles SiO2-g-PDAC decreases with raising temperature.