Previous work mainly focused on investigations of computational model and using numerical simulation method, this method is limited in study of hydrocyclone due to the impact of simplification of boundary condition and turbulent models. In light of this, this paper designed an experimental strategy for industrial hydrocyclones on classification of fine iron ore tailings. The paper studied the classification efficiency of industrial hydrocyclone for fine iron ore tailings. The study analyzed the effect of hydrocyclone diameter and underflow diameter on the classification efficiency. The analysis primarily focused on the effect of structural variation of underflow in hydrocyclones with different diameters on underflow solid phase productivity, Newton comprehensive classification efficiency, and underflow granularity composition. The experiment results showed that the size of hydrocyclone had great influence on the performance of the hydrocyclone, which provided basis on the selection of hydrocyclone, as well as structural design and optimization.