Influence of the Casimir-Polder force on a slowly moving atom near a left-handed slab is discussed. We focus on an initially excited atom and its dynamic evolution during the spontaneous decay process. The left-haned slab is adopted based on two factors: (1) It provides a relatively stronger Casimir-Polder force on the excited atom far away from the interface, and (2) it can lead to an inhibited spontaneous decay rate within such a region. Therefore, we can discuss the dynamic evolution of atoms acted only by the Casimir-Polder force. The dynamic evolution discussed here includes both the evolution of atomic population and the atomic displacement. As the Casimir-Polder force depends on the atomic population, while the decay rate is related to the atomic positions, the atomic dynamic evolution is determined by its initial conditions, i.e. its position and volecity. We choose two initial positions for discussion, i.e. (1) the position with the maximum resonant Casimir-Polder force, and (2) the edge of the resonant Casimir-Polder force of the atom with dipole parallel to the interface. Furthermore, we also consider two kinds of orientations of atomic dipole, i. e. parallel and normal to the interface. It is found that the atom can be repulsed away from a surface by the Casimir-Polder force with a proper initial velocity in certain dipole orientaion during the sponatneous decay process. As the atomic dynamics depends on the orientation of the atom dipole momentum, our result can be used as a reference to distinguish atoms with different dipole momenta. Though the force discussed here exists during the spontaneous decay process, it is much different from the recoil force of the atom when it emits a photon during the spontaneous decay. The statistical average of the recoil force is null, but that of the resonant Casimir-Polder force is not. After reasonable estimation, such a Casimir-Polder force can counteract the thermal fluctuation of temperature of 15 μupK during sponatneous decay. If combined with other constraint methods, it is helpful to control the dynamics of an atom more efficiently.