  We propose a new interpolating field for S$_{11}$(1535) to determine its mass
from QCD sum rules. In the nonrelativistic limit, this interpolating field
dominantly reduces to two quarks in the s-wave state and one quark in the
p-wave state. An optimization procedure, which makes use of a duality relation,
yields the interpolating field which overlaps strongly with the negative-parity
baryon and at the same time does not couple at all to the low lying
positive-parity baryon. Using this interpolating field and applying the
conventional QCD sum rule analysis, we find that the mass of S$_{11}$ is
reasonably close to the experimentally known value, even though the precise
determination depends on the poorly known quark-gluon condensate. Hence our
interpolating field can be used to investigate the spectral properties of
S$_{11}$(1535).
