The problem of slope stability is considered as a main geotechnical problem due to the significant damage (material or moral) related to failure. This paper aims to study the influence of piles on the stability of slopes loaded with strip footing and investigating the parameters affected on stability (location of pile row relative to the slope crest X , piles spacing S , piles length L and edge distance of the footing b ). This study has been realized in two phases : the first phase consists in establishing a numerical model for sand slope by using finite element analyses program (FLAC3D) and determining the footing settlement at crest of slope before using piles and after reinforcing , after that the numerical results is compared with the experimental ones (reference case ). A close agreement between experimental and numerical curves is noticed .The second phase deals with studying the influence of most important parameters such as ( piles length ,piles spacing, pile row location relative to the slope crest on stability and edge distance of the footing) on the slope stability. The results of parametric study have shown the piles installed near the slope crest is more efficient in reinforcing where the safety factor is increased by reducing the distance between row of piles and slope crest and the greatest value for safety factor when X=0.7Lx . The currently study showed the efficiency of piles to increase the ultimate bearing capacity with increasing edge, after that at b=3B the increase in ultimate bearing capacity decreased. Also the slope stability depends significantly on pile length and it increases even reaching the length equals the height of the slope. At other hand, the safety factor is reduced by increasing the piles spacing, so that the efficiency of pile is disappeared when pile spacing equals to six times pile diameter(UBCR<1.1).