  The influence of Unruh effect on the quantum and classical correlation of a
quantum entangled state is investigated, when one or two of the observers are
accelerated. It is found that the quantum and classical correlation would
approach to a finite value with the increase of the acceleration when only one
observer is accelerated, but they would decrease to zero quickly when two
observers are accelerated. The latter result implies that the gravitational
field would break the correlation obviously when the acceleration is caused by
the gravitational field. Thus, when the two observers stay in the gravitational
field, the quantum or classical correlation would not easy to be preserved for
a long time.
