An improved two-temperature model is proposed to characterize the ablation of thick metal aluminum by multi-pulse femtosecond laser, and the model is proved in experiments. In order to achieve hole-drilling with high ratio of depth-diameter, three dimensional numerical simulation to the temperature field in the process of femtosecond laser ablation on metal aluminum surface is carried out. The aperture and depth of hole are predicted with different laser parameters, such as laser energy density, pulse number, laser waist radius and so on. The experiments show that the laser energy density and pulse number are the main factors affecting the morphology of holes, and the multi-pulse ablation threshold is much lower than the single-pulse one. The non-diffraction characteristics of aquasi Bessel beam within the maximum collimating distance are discussed and the enhancement on hole-drilling processing of Bessel beams is analyzed.