Time-resolved measurements of plasma plume emission spectra with pulsed laser ablation of metal Cu at different krypton pressure were reported.Taking pictures with speedy and synchronized photography,photos of optical plasma plume from laser ablation of metal Cu at different krypton pressure were obtained.The experimental results indicate that the plasma plume emission spectra were composed of atomic spectral lines,and the plasma plume colour changed with the ambient gas pressure.The effect of ambient gas pressure on the plasma plume excitation radiation mechanism in pulsed laser ablation of copper was discussed.The results areexplained using a simple model based on the fact that the plasma plume main excitation radiation mechanism is changed with ambient gas pressure.The main excitation radiation mechanism in plume is electron collision energy transfer at low pressure,is electron collision energy transfer excitation radiation and recombination excitation radiation of electrons and ions at middle pressure,and is recombination excitation radiation of electrons and ions at high pressure.The model can be used to explain the experimental results qualitatively.