In the process of laser ablation, the target′s absorption coefficient, thermal conductivity, density and surface reflectivity are dependent on its temperature. When the target surface temperature approaches the thermodynamic critical temperature Tc, the high-temperature part of the target transits from metal to nonmetal. The target is divided into two temperature regions (below and above 0.8Tc) and a model is built up to calculate the above physical parameters. The temporal and spatial distribution of temperature, absorption coefficient and thermal conductivity of Al target are obtained by a one-dimensional heat conduction equation. Ablation depth is calculated as a function of laser pulse energies. Numerical results are in good agreement with the experimental results, which validate the presented model.