Employing Q-modulating YAG pulse laser as source, using metal Cu as sample, using CCD detector to collect the transient spectrum and using Boltzmann distribution method, the temperature of the laser plasma is measured. From the results we know when the laser pulse energy is 100mJ, Cu spectrum mainly consists of atomic excitation lines and its temperature is 14063.8K. This work has great potential for investigating the interaction processes between laser and matter.