Erosion is one of the main factors of destruction of hydraulic structures. Therefore, soil improvement is necessary to improve soil quality and reduce soil erosion. Due to the adverse effects of substances such as lime and ash and also the increasing usage of nanotechnology in various branches of engineering sciences, using nanoparticles as new additives is an efficient way. In this study, to investigate the effect of nanosilica additive on soil, erosion function apparatus (EFA) is used. Samples containing nanosilica with 0, 1, 1.5, 2 and 4 percent (w/w) of dry soil were compacted in the standard compaction mold. They were tested in a close flume and with variable discharges. Erodibility parameters showed that by addition of 1.5% nanosilica to the dry soil, erodibility decreased by 92% as compared with untreated soil. The optimal amount of nanosilica was chosen as 1.5%. The results showed that samples compacted with the optimum moisture content causes the least erodibility. Scanning Electron Microscope (SEM) tests results showed that by addition of nanosilica to the dry soil, soil structure becomes more dense which reduces the risk of erosion.