  Supersymmetric Ward identity for the low energy effective action in the
standard background gauge is derived for {\it arbitrary} trajectories of
supergravitons in Matrix Theory. In our formalism, the quantum-corrected
supersymmetry transformation laws of the supergravitons are directly identified
in closed form, which exhibit an intricate interplay between supersymmetry and
gauge (BRST) symmetry. As an application, we explicitly compute the
transformation laws for the source-probe configuration at 1-loop and confirm
that supersymmetry fixes the form of the action completely, including the
normalization, to the lowest order in the derivative expansion.
