  In this paper, spinor and vector decomposition of SU(2) gauge potential are
presented and their equivalence is constructed using a simply proposal. We also
obtain the action of Faddeev nonlinear O(3) sigma model from the SU(2) massive
gauge field theory which is proposed according to the gauge invariant
principle. At last, the knot structure in SU(2) Chern-Simons filed theory is
discussed in terms of the $\phi$--mapping topological current theory. The
topological charge of the knot is characterized by the Hopf indices and the
Brouwer degrees of $\phi$-mapping.
