  We have studied relationship between local lattice disorder, Ru 4$d$
spin-orbit interaction, and global spin/orbital orders of
Ca$_{2-x}$Sr$_x$RuO$_4$ in the Sr-rich and Ca-rich regions of its phase diagram
by using unrestricted Hartree-Fock calculation on a $8\times8$ RuO$_4$ lattice
model. The calculations show that the local elongation of RuO$_6$ octahedron in
an antiferromagnetic insulator Ca$_2$RuO$_4$ induces local orbital change with
making the Mott gap narrower. On the other hand, local compression of RuO$_6$
octahedron in a paramagnetic metal Sr$_2$RuO$_4$ induces global
antiferromagnetic or ferromagnetic states. This result is consistent with a
recent systematic $\mu$SR study by Carlo {\it et al.} which has revealed the
static antiferromagnetic order at low temperature in the Sr-rich region.
