The effect of cations(Na+, Ca2+) on the storage stability of anionic emulsified asphalt were studied by adding electrolytes of NaCl and CaCl2 to anionic emulsified asphalt. Zeta potential, particle size distribution and microstructure of anionic emulsified asphalt with or without electrolyte added were determined to analyze the impact mechanism. Results show that Na+ has no significant effect on the storage stability of anionic emulsified asphalt, but Ca2+ has remarkable adverse effect on the storage stability of anionic emulsified asphalt, and the degree of influence is enhanced by increasing Ca2+ concentration. The reasons for that are the adsorption and aggregation of Ca2+ on the surface of asphalt particles, and reduction of the electrostatic repulsion between the asphalt particles causing aggregation of asphalt particles. Thus, the Ca2+ concentration in the water used for producing anionic emulsified asphalt shouldnt exceed 1.9mmol/L, and the additives which could ionized to form Ca2+ shouldnt be used.