Spin-valves (SVs) constitute a significant class of magnetic metal structures with a large range of technological applications. This class of structure offers interesting magnetic properties due to their alternation with the non-magnetic layers. The SVs fortunately have good magnetic properties at room temperature (RT). This study intends to use Boltzmann Approach–BA, to treat the magetotransport properties of Co-based SV. Outer-surface scattering effects on magnetoresistance (MR) performance encountered in these structures are investigated by varying the interfacial chemical composition. Analysis of the results reveals the existence of a significant improvement of magnetic phenomenon for a scattering that is more and more specular of the conduction electrons through outer-surface. A giant MR (GMR) of amplitude 136.9 % is obtained for an interfacial geometric roughness of magnitude 2 Å. The GMR ratio is the result of large asymmetry in the spin-dependent interfacial scattering and a completely specular outer-surface scattering.