At present, conventional low-temperature superconductors such as Nb 3 Sn strands have been extensively applied in high-energy and nuclear physics, as well as in magnetic resonance imaging systems. In this paper, a 3D finite element model considering sophisticated structure of superconducting filament bundles and metal matrix elements is built to deal with the electromagnetic behaviors of a Nb 3 Sn strand exposed to tension and bending loads. The mechanical constitutive relations of filament bundles and metal matrix are described with elastic and elasto-plastic axial stress-strain curve, respectively. The voltage-current characteristic of the metal matrix elements is determined with the Ohmic law, and that of the superconducting filaments follows the n power relation. The stress-strain state is simulated and then implemented in the electromagnetic model, through the scaling law of ITER Nb 3 Sn strand. We find that the plasticity of copper and the twist filaments cause the enhanced inhomogeneous strain profile in a strand composite, compared to the strain profile in a strand with untwisted filaments. We also discuss the current/field profile, critical current degradation, and AC loss in the strand composite under the tension and bending loads.