  The global chiral symmetry of a $SU(2)$ gauge theory is studied in the
framework of renormalization group (RG). The theory is defined by the RG flow
equations in the infrared cutoff $\L$ and the boundary conditions for the
relevant couplings. The physical theory is obtained at $\L=0$. In our approach
the symmetry is implemented by choosing the boundary conditions for the
relevant couplings not at the ultraviolet point $\L=\L_0\to\infty$ but at the
physical value $\L=0$. As an illustration, we compute the triangle axial
anomalies.
