Abstract: The velocity autocorrelation function and the spectral density of LiCL melt and LiCL glass have been calculated based on the phase orbit obtained from molecular dynamics simulation. The results showed that the spectral densities of both melt and glass can be described as a linear combination of those damped oscillation and Brownian motion. So the movement of ions in LiCL system can be regarded roughly as the superposition of the damped oscillatory motion and Brownian movement. The coulombian force existed in LiCL system made the oscillatory motion more stronger than that in other liquide. It is found through the calculation, the higher the temperature the intenser the Brownian motion and the lower the ω value of the peak of Ψ(ω).