The key to improving the quality of thin film prepared by pulse laser deposition, is to properly control the electron-phonon coupling relaxation time which determines the pulse duration and the laser fluence. Taking the aluminum targets as an example, we obtain the evolution temperature of electron subsystem and ionsubsystem by solving the standard two temperature equation using the finite-difference time-domain (FDTD) method. Then, we obtain the electron-phonon coupling relaxation time, which can distinguish between the thermal ablation and the non-equilibrium ablation to ensure that we can control the process of pulse laser ablation well. In addition, we find out how does the electron-phonon coupling relaxation time change with the pulse duration and the laser fluence.