Several properties of Bose-Einstein condensed atoms confined in a double well potential(DWP) are investigated, which include the tunneling effect, interference of the condensed atoms and the dynamics of the atom-standing wave laser field system. It is shown that, in such a DWP, the average number of condensed atoms in the two traps is still same in presence of tunneling effect, this ensures the visibility of interference fringes of atoms. The interference fringes are closely related to the difference and sum of atomic wave packet of the two traps. Moreover, the present result manifests that the tunneling effect can obviously affect the dynamics properties such as wave function, energy spectrum of the atom-standing wave laser field system.