  A new idea of the cosmological constant is proposed in this paper. Due to the
horizon is limited, the quantum fluctuation of the inflaton field is not zero,
a nonzero vacuum energy is remained as a residual inflationary energy of an
unusual potential, however the true stable vacuum energy is zero fortunately. A
unified model of the cosmological constant and the chaotic inflation is
proposed, which satisfies almost all cosmological phenomenology and will can be
tested by data of the cosmic large scale structure.
