Abstract: The characterization and mechanism of the adsorption of human serum albumin (HSA) on silicon-substituted hydroxyapatite (Si-HA) were studied. A Langmuir adsorption isotherm and the apparent activation energy were obtained by analyzing the kinetic properties of the adsorptive reactions. The results show that the apparent activation energy of the adsorption of HSA on Si-HA and HA is 21. 28 kJ· mol^-1  and 35. 57 kJ· mol^-1 respectively and the rate constant of adsorption reaction is 1.48 and 1.34 min^-1 respectively at 20℃. The adsorptive capacity of HSA on Si-HA is stronger than that on HA. The adsorptive mechanism was also investigated by XRD，FTIR and fluorescence spectrum. The results indicate that the adsorptive action is mainly the chemical adsorption including physical adsorption. The adsorption differences are presented by analyzing the molecular structure of Si-HA and HA，which may pave the way for the study on biocompatibility of Si-HA and HA.