Based on the quantum dynamics of laser-ion interaction beyond the Lamb-Dicke limit，we discuss how to superpose a series of vibrational number states from motional ground state by sequentially applying laser beams. The Q function，Wigner distribution function，and the nonclassical properties such as squeezing effect and anti-bunching effect of the generated superposition states are investigated in detail by numerical method. It is shown that，by controlling the durations of the applied laser pulses，these quantum states could well approach to the well-known coherent states.