  We present for the first time the nonlinear diffeomorphism in the Randall
Sundrum model that can keep the effective Lagrangian invariant in any order of
expansion. We will show that the off-shell diffeomorphism shapes the
interaction structure. However the radion mass is in fact protected by an
on-shell diffeomorphism, which can be spontaneously broken by the
Goldberger-Wise mechanism. The nonlinear property of diffeomorphism also
ensures a unique radion field even in the extension of RS model with
intermediate branes.
