Abstract: In this paper, the roles of Ca2+ and natural surfactants in the oil sands water-based separation process were analyzed by AFM through quantitative description of the interaction behavior between the asphalt and silica surface. The effect of calcium cations, natural surfactants, and their combination on the asphalt and silicon surface interaction in different solution environment was investigated. The results show that in acidic aqueous environment, silica surface adsorbed cationic natural surfactant becomes to be hydrophobicity, the long-range force between asphalt and silica becomes a weak repulsive force and a strong adhesive force. Addition of calcium divalent ions makes both the long range force and adhesive force decrease due to the adsorption of Ca2+ on the surface of SiO2 and compression of the surface electric double layer. At strong alkalis condition, the Ca2+ is dissociated to form hydrolyzate CaOH+, which compresses the surface electric double layer and reduces its electronegativity. The anionic surfactant is adsorbed on outer layer of CaOH + through electrostatic interaction. This enhances the hydrophobicity of the silica surface, therefore, the long-range force between asphalt and silicon becomes attractive force from repulsive force and the cohesive force increases with the increase of Ca2 + concentration. These force curves can be reasonably explained through the changes of Zeta potential value of asphalt droplets and silica particles.