Abstract: n order to avoid the agglomeration of nano-sized CaCO₃ in water，biodegradable modified polyepoxysulfosuccinic acid was used as the dispersant.Due to its structural unit containing strong polar sulfonate acid group，the electrostatic repulsion force among particles in the suspension was increased.When it was employed as dispersant，nano-sized CaCO₃ slurry had better stability，smaller particle size，and better flowability compared with unmodified polyepoxysulfosuccinic acid.When co-operating with sodium tripolyphosphate，which used as the assistant dispersant，the dispersion effect of modified polyepoxysulfosuccinic acid on nano-sized CaCO₃ were obviously increased.

Key words: nano-sized CaCO₃, dispersibility, modified polyepoxysulfosuccinic acid