  In this paper, we first deduce a formula of S-curvature of homogeneous
Finsler spaces in terms of Killing vector fields. Then we prove that a
homogeneous Finsler space has isotropic S-curvature if and only if it has
vanishing S-curvature. In the special case that the homogeneous Finsler space
is a Randers space, we give an explicit formula which coincides with the
previous formula obtained by the second author using other methods.
