To investigate the effect of iron oxides on consistency limits of clayey soil, the ordinary clay from Guilin was selected as the parent soil for this study, and mixed soil samples of iron oxides and NaNO₃ as well as soil samples added with NaNO₃ alone were prepared. Tests were conducted to study the variation of consistency limits under different temperature and dosage conditions, and the particle size analysis and microstructural test were conducted to explain the mechanism of iron oxides’ influence on soil particles. The test results showed that NaNO₃ reduced the consistency limits of Guilin clay. The greater the dosage was, the more obvious the reduction in consistency limits was. The trends of liquid limit, plastic limit and shrinkage limit changes were consistent. Iron oxides increased the liquid limit, plastic limit and shrinkage limit of Guilin clay after the addition of NaNO₃, and the liquid limit increased the most, followed by plastic limit and shrinkage limit. This enhancement effect intensified with the increase of iron oxide concentration and weakened with the rise of temperature. After drying the mixed soil at 105 ℃ for 48 hours, the effect of iron oxides on liquid limit, plastic limit and shrinkage limit was nearly eliminated. High-temperature drying alters the interaction between iron oxides and soil particles and affects the particle size, thereby influencing the consistency limits of soil.