  Irregular conformal block is motivated by the Argyres-Douglas type of N=2
super conformal gauge theory. We investigate the classical/NS limit of the
irregular conformal block using spectral curve on a Riemann surface with
irregular punctures, which is equivalent to the loop equation of irregular
matrix model. The spectral curve is reduced to the second order (Virasoro
symmetry, $SU(2)$ for the gauge theory) and third order ($W_3$ symmetry,
$SU(3)$) differential equations of a polynomial with finite degree. The
Virasoro and W symmetry generate flow equations in the spectral curve and
determine the irregular conformal block, hence the partition function of the
Argyres-Douglas theory ala AGT conjecture.
