Optical emission of plasma is used to investigate the characteristics of dynamics distribution in the plume generated by ablation of a SiC sample using Nd:YAG laser. The plume expansion dynamics is characterized by time-of-flight measurement.We find that the profiles of Si (Ⅰ) (390.55nm) split into two components and the Si (Ⅱ) (634.71 nm) spectra show two distinct expansion dynamics regions.The time-of-flight measurement of Si(Ⅱ)(634.71 nm) under different laser irradiance conditions,from 0.236 GW/cm2 to 1.667 GW/cm2,are presented and discussed.