Partition curves are widely used to determine the spiral separator efficiency. In this work, the partition curves were used in order to investigate the particle transportation to concentrate and tailing streams. Simulation of fine particle removal using the size-by-size partition curves showed that the recovery of gangue particles to concentrate can decrease 8.7%. It also showed that the recovery of valuable particles would increase by 6.5% and reaches 90%. Therefore, pilot-scale tests were conducted to verify the simulations. After removal of fine particles from the feed of spiral separator and treating the removed materials with high-intensity magnetic separator, total mass recovery, iron recovery, and iron grade increased from 71%, 85%, and 54% to 80%, 91%, and 56%, respectively.