  By making use of Duan-Ge's decomposition theory of gauge potential and the
Duan's topological current theory proposed by Prof. Duan Yi-Shi, we study a two
component superfluid Bose condensed system, which is supposed being realized in
the interior of neutron stars in the form of a coexistent neutron superfluid
and protonic superconductor. We propose that this system possesses vortex
lines. The topological charge of the vortex lines are characterized by the Hopf
indices and the Brower degrees of $\phi$-mapping.
