Chemical flooding is technically feasible to increase oil recovery from depleted sandstone reservoirs with low pressure. Polymer-surfactant flooding is a potential process in the chemical flooding methods for enhanced oil recovery (EOR) in sandstone porous media. However, chemical additive cost and surfactant loss due to adsorption on the reservoir rock are the main concerns in this type of EOR processes. This paper presents adsorption equilibrium of a natural surfactant, Zyziphus spina-christi, onto a real sandstone reservoir. Batch adsorption experiments were carried out to figure out the impacts of adsorbent dose on adsorption performance. The equilibrium adsorption data were analyzed with two common adsorption models and it was found that the Freundlich model is a pretty good fit for adsorption equilibrium of Z. spina-christi based on the value of determination coefficient (R-2). Results from this study are instructive for appropriate selection of surfactants in design of EOR processes and reservoir stimulation plans for sandstone reservoirs.