Stable ASA Pickering emulsions were prepared by using montmorillonite clay- particles modified by silane coupling agent KH570 as the particulate emulsifier of ASA and water,and the effects of pH value,oil- to- water ratio and particle concentration on the stability and sizing performance of the emulsions were investigated.The results indicate that the presence of modified montmorillonite remarkably improves the stability of ASA emulsions,that the stability first increases and then decreases with the increase in pH value and reaches the maximum at pH 7.0,that a phase inversion from an oil- in- water (O/W) emulsion to a water- in- oil (W/O) emulsion may occur at a oil- to-water ratio of 3:1,that the particle concentration is tightly related to the formations of the particle film at oil- water interface and the clay particle network in water,that higher particle concentration results in smaller droplet size andhigher stability of ASA emulsions,that the optimal particle concentration for ASA emulsions ranges from 1.5% to 2.0%,and that both the stability to hydrolysis and the sizing performance of ASA emulsions greatly improve due to the employment of modified montmorillonite.