In this study, the inhibitor effect of ampicillin sodium salt on carbon steel corrosion in 1M of HCl solution was investigated. The experiment was carried in HCl solution different temperature (303,313, and 323) K and by used different inhibitor concentration, the weight loss and polarization curve investigation were done. The activation energy, heat od adsorption and thermodynamic parameters of inhibition effect of Ampicillin sodium salt under investigation on the corrosion process have been calculated at different temperature. It was found the effect of inhibitor was decrease with increasing temperature and Ampicillin sodium salt as a mixed inhibitor for the corrosion of carbon steel. The inhibition efficiency of Ampicillin sodium salt increases-almost-with temperature and the activation energy decreases in presence of the inhibitor. The inhibitor efficiency increased by increasing inhibitor concentration.