Abstarct: This experimental study aimed to investigate the effects, behavior and local bonds between ultra high performance concrete and steel bars by the Nano Sillica presence. Considering the previous studies reveals that an experimental study in this field is necessary. The experimental Pullout test is baxsed on the RILEM standard. Pullout test is The oldest, easiest, cheapest and least time-consuming way to determine the local bond's stresses. The study managed to investigate the bond's stress between the ultra high performance concrete and steel bars by two categories: 1-different bar diameters (12 and 14) and 2-concrete's cover (db, 2db,3db and 4db) over 96 samples. Experimental studies are the keys to complicated cases, where analytical methods are incapable of solving the problem due to the complexities associated with it. The Nano-sillica's behavior on the local bonds between ultra high performance concrete and steel bars is of such issues. Interaction among concrete, steel bars and Nano-sillica, steel bar's yielding, concrete's cracking, stresses redistribution and element's bearing incapability due to crushing or yielding, are some samples that reveals the problem complexities. However, the experimental studies, provides further information about the behavior of the Nano-Sillica's effects on local bonds between ultra high performance concrete and steel bars.