  The theoretical research of the origin of magnetic skyrmion is very
interesting. By using decomposition theory of gauge potential and the gauge
parallel condition of local bases of $su(2)$ Lie algebra, its $SU(2)$ gauge
potential is expressed as flat connection. As an example of application, we
obtain the inner topological structure of second Chern number by $SU(2)$ flat
connection method. It's well known that if magnetic monopole exists in
electrodynamics, its Wu-Yang potential is indispensable in $U(1)$ invariant
electromagnetic field. In $2$-dim magnetic materials, we prove that if magnetic
skyrmion exists, its integral kernel must be $U(1)$ Wu-Yang curvature, where
its $U(1)$ Wu-Yang potential is the projection of $SU(2)$ flat connection on
$su(2)$ local Cartan subalgebra. The magnetic skyrmion can be created by
performing concrete $SU(2)$ local gauge transformation to $su(2)$ Cartan
subalgebra $\sigma_3$. The components of the $U(1)$ Wu-Yang curvature
correspond to the emergent electromagnetic field of magnetic skyrmion
