The use of geosynthetic materials as reinforcement in geotechnical engineering works is significantly increasing over the past decades. Geogrid, whose primary functions is reinforcing the soil mass, is one of the geosynthetics that has been used. In a reinforced soil structure, there are different types of interaction between soil and geogrid. To be possible to obtain reliable design parameters is essential to know the mobilized mechanisms in the interaction. This situation has been investigated by many researchers, but there are still many aspects to be better understood about geogrid reinforced soil behavior. In this research, numerical tools have been used to improve our knowledge about reinforced soil techniques. Numerical modeling of triaxial and direct shear tests on reinforced and non reinforced soils were carried out using software Plaxis. It was verified the resistance and stiffness increase of the soil due to geogrid inclusion and the interface soil-reinforcement resistance parameters. To calibrate the software and to validate the numerical analyses, back-analyses of the tests carried out by Sieira (2003) were done. These results helped to define important aspects to the tests modeling such as geometry and tests boundary conditions. The numerical analyses of the triaxial tests suggest that the software Plaxis reasonably allow an adequate reproduction of the reinforced soil tests. It was possible to foresee the increase of soil resistance because of reinforcement inclusion. In addition, an alternative analysis, where one applies a confining stress that reproduces the reinforcement influence, it was done. Numerical analyses of non reinforced direct shear tests had numerically evidenced the rotation of the axis of the principal stresses directions and the presence of a central zone of shear (shear zone). The soil- geogrid interface resistance was not well reproduced, indicating that Plaxis does not allow this type of evaluation. To inclined reinforcement relative to failure plane, it was verified the maximum gain of resistance is achieved with inclined reinforcement at 60º and when rigid geogrids are used.