Using molecular dynamics simulations, we investigated the process of oil detachment from silica surface modified by carboxy groups in aqueous surfactant (cetyltriethylammonium bromide (CTAB)) solution. It is demonstrated that CTAB molecules promote the formation of water channel between oil molecules and silica surface, which is vital to the detachment of oil drop from silica surface. In this paper, the effects of temperature, surfactant concentration, and calcium ion concentration on the oil detachment from silica surface have been extensively examined. We find that appropriate temperature, surfactant concentration, and calcium ion concentration are crucial for improving oil detachment efficiency. Our study can provide a simple method to design and choose appropriate oil-displacing agents, which is important for its applications in oil recovery, ore floatation, detergency, printing fields, and so on. (C) 2015 Elsevier B.V. All rights reserved.