Abstract: The main component of sludge particles in the secondary side of steam generator (SG) of PWR nuclear power plant was iron oxide. The dispersion effect of polyacrylic acid (PAA) on Fe₃O₄ and Fe₂O₃ iron oxide particles was investigated by static sedimentation tests. The results show that the sedimentation rate of Fe₃O₄ and Fe₂O₃ particles slowed down with PAA addition, and it showed better on Fe₃O₄ particles. The dispersion effect of PAA on iron oxide particles increased with the decrease of particle size, and PAA had obvious dispersion effect on Fe₃O₄ particles with particle size below 12 μm. The effective mass concentration of PAA to maintain high dispersing effect on iron-based particles was quite wide, ranging from μg/L to mg/L. PAA had obvious dispersing effect on SG real sludge in particle size less then 28 μm, and the addition of PAA improved its suspension efficiency from 34.05% to 56.93%.