Topologically non-trivial classical solutions and their roles in the Big-Bang cosmology are studied. Zero-mode appears in the vortex background, and play the role of carrying persistent electromagnetic current. In this way the vortex coupled to fermions becomes superconducting sting, which generate observable effects in astrophysical magnetic field. The model that the string provide the seed for galaxy formation is analytically investigated by using dynamical equation of string in more detail, and the constraints of it are calculated to be consistent with the experimental results. We also examine the role and fate of the superconducting string in the Vilenkin``s string dominated universe scenario.