Adsorption of soybean oil Silica particles modified by cationic polymer (Polyethyleneimine, PEI) was studied. Zeta potential result shows an increase in positive charge on the surface of modified silica particles. The effects of various parameters on oil adsorption such as PEI concentration, pH, electrolyte concentration, and temperature were investigated. It was found that PEI enhances an adsorption of soybean oil on PEI-modified silica particles. The soybean oil adsorption on the modified silica increased with respect to PEI concentrations. It was revealed that the higher pH, the more soybean oil can be adsorbed on PEI-modified silica surfaces. The electrolyte and high temperature reduces the soybean oil adsorbed on the PEI-modified silica particles.