  We investigate the evolution process of the interference pattern for a
coherent array of Bose-Einstein condensates in a magnetic trap after the
optical lattices are switched off. It is shown that there is a decay and
revival of the density oscillation for the condensates confined in the magnetic
trap. We find that, due to the confinement of the magnetic trap, the
interference effect is much stronger than that of the experiment induced by
Pedri et al. (Phys. Rev. Lett, {\bf 87}, 220401), where the magnetic trap is
switched off too. The interaction correction to the interference effect is also
discussed for the density distribution of the central peak.
