We successfully label-free and real-time detecte the interactional dynamic processes of rabbit IgG with different concentrations (1.25 mg/mL, 2.50 mg/mL and 5.00 mg/mL), and goat anti-rabbit IgG with a concentration of 0.02 mg/mL by the oblique-incidence reflectivity difference method (OIRD). The dynamic curves and times of interaction, response to concentration of rabbit IgG, are obtained. The experimental results demonstrate that the OIRD method can not only can distinguish the biomolecular interactions, but also real-time detect the interactional dynamic processes of biomolecules, indicating that the OIRD method has promising and extensive applications for the investigating of biomolecular interactions.