  We investigate polarization of high-energy emissions from the Crab pulsar in
the frame work of the outer gap accelerator, following previous works of Cheng
and coworkers. The recent version of the outer gap, which extends from inside
the null charge surface to the light cylinder, is used for examining the
synchrotron radiations from the secondary and the tertiary pairs, which are
produced outside the gap. We calculate the light curve, the spectrum and the
polarization characteristics, simultaneously, by taking into account gyration
motion of the particles. The polarization position angle curve and the
polarization degree are calculated to compare with the Crab optical data. We
demonstrate that the radiations from inside the null charge surface make
outer-wing and off-pulse emissions in the light curve, and the tertiary pairs
contribute to bridge emissions. The emissions from the secondary pairs explain
the main features of the observed light curve and spectrum.
  On the other hand, both emissions from inside the null charge surface and
from the tertiary pairs are required to explain the optical polarization
behavior of the Crab pulsar. The energy dependence of the polarization features
is expected by the present model. For the Crab pulsar, the polarization
position angle curve indicates that the viewing angle of the observer measured
from the rotational axis is greater than $90^{\circ}$.
