The use of passive inclusion for soil reinforcements, technique usually known as soil nailing, has been gaining growing acceptance within civil engineering professionals,especially in Rio de Janeiro. However this technique lacks a more detailed study on the elevant parameters influencing the deformability of soil nailed masses. The nails are rigid inclusions, sub horizontally positioned, without tension or free space between the nail and the surrounding soil mass. The axial forces on the nails are developed due to lateral decompression caused by soil excavation. As the excavation stages proceed, the nails are successively being installed, producing a reinforced zone, which acts as a support for the soil mass. The frontal face of the excavation is usually protected by shotcrete, and has no structural functions. This research aims at evaluating the influence of the various geotechnical and geometric parameters on the stress strain behavior of nailed excavations, with vertical face and horizontal soil surface. The parametric analysis was performed using FLAC (Fast Lagrangian Analysis of Continua), which is a computer program based on the finite difference method. This program simulates bi dimensional behavior of reinforced structures of soils and or rocks,which may be submitted to plastic flow when the strength limit is reached. The results show that the Youngs modulus (E) and soil cohesion (c ) have a very significant influence on the displacement of a soil nailing structure. The analysis also indicates that the mobilized shear strength at the soil nail interface (qs) is also an important parameter, particularly for nail lengths (L) smaller than 0,80 of the excavation height (H) (L/H < 0,80). It is therefore recommended that qs be directly determined by pullout in situ tests. Regarding nail inclination the results suggests no significant influence on the reinforced soil mass displacement for alpha less or equal than 10 degrees. These results are particularly relevant for engineering practice, because a 10 degrees inclination facilitates grouting injections in the field. The results in this research indicates the use of nail lengths (L) greater than 0,70 of the excavation height (H) (L/H greater than 0,70) in soil nailing technique.