Based on molecular dynamics， the models of emulsified asphalt system without salt and with salt were established， and the effect of metal cations on the stability of sodium dodecyl sulfate （SDS） anionic emulsified asphalt was studied. The effect of Ca²⁺/Mg²⁺ on the stability of emulsified asphalt systems was analyzed by the relative concentration distribution， the molecular inclination of the emulsifier and the interaction energy between the facets of the emulsions. The results show that compared with the system without salt， the addition of Ca²⁺/Mg²⁺in the salt-containing system would reduce the adsorption capacity of the interfacial film， and the binding energy between the asphalt phase and the aqueous phase， lead to the instability of the emulsified asphalt system. The calculated results of molecular simulation are consistent with the experimental conclusions， verifying the correctness of the model.