  We discuss the dimensional reduction of five-dimensional supergravity
compactified on S^1/Z_2 keeping the N=1 off-shell structure. Especially we
clarify the roles of the Z_2-odd N=1 multiplets in such an off-shell
dimensional reduction. Their equations of motion provide constraints on the
Z_2-even multiplets and extract the zero modes from the latter. The procedure
can be applied to wide range of models and performed in a
background-independent way. We demonstrate it in some specific models.
