  We study the phase diagram of S=3/2 and S=2 bond-alternating spin chains
numerically. In previous papers, the phase diagram of S=1 XXZ spin chain with
bond-alternation was shown to reflect the hidden $Z_{2}\times Z_{2}$ symmetry.
But for the higher S Heisenberg spin chain, the successive dimerization
transition occurs, and for anisotropic spin chains the phase structure will be
more colorful than the S=1 case. Using recently developed methods, we show
directly that the phase structure of the anisotropic spin chains relates to the
$Z_{2}\times Z_{2}$ symmetry.
