[en] Energy absorption of intense Nd:YAG laser pulse at the surface of aluminum was measured as a function of laser energy fluence φ by photoacoustic method using a piezoelectric transducer. Luminescence spectra from laser induced plume were measured. A Q-switched Nd:YAG laser which generate pulses of 8 ns duration was used. Photoacoustic signal intensity I increased according to the laser pulse energy at low fluences. At a constant pulse energy, the I was a function of the energy fluence φ and had a threshold φ_th. When the φ was lower than the φ_th, the I was constant and corresponded to the absorption coefficient of the metal. Above the φ_th, it approached the maximum I_max and then began to decrease with further increase in the φ. If the authors represent the relative change in I at different pulse energies as the normalized intensity I/I_max, a universal curve was obtained. Below the φ_th, the process was normal photon absorption by the metal. Damage left on the irradiated surface became evident above the φ_th. Above the φ_th and below the I_max, surface temperature increased high enough to form melt and the photo-absorption coefficient would increase during one laser pulse. A shock wave would be formed at the surface and contribute to the increase of the I. Higher φ than at the I_max, some processes which inhibit the energy absorption would occur and the I would decreased