Abstract: A static force model was proposed for the above emulsion systems and the effects of concentration of salts and interfacial zeta potential on emulsion stability were analyzed with this model. The contradiction between experimental phenomena and modeling results was explained. It was pointed out that during the collision of two liquid droplets in the presence of interfacial zeta potential the interfacial surfactant molecules on the two approaching droplets repelled each other so strongly that it leads to the coalescence between these two droplets.