Abstract: Theoretical analysis and numerical calculations have been perfofrmed toinvestigate the laser impulse coupling to aluminium targets irradiated in vacuum. The re-sults presented are obtained on the basis of the mathcmatical model including heatconduction,vaponzation and plasma ignition. The significant role of a correct descrip-tion of the vaporization process is shown. It is found also that the two-photonionization results in increasing the initial electron number density and their temperature.This,in the long run, results in increasing the excited atoms number density, and therate of electron origination at the expense of their photoionization grows accordingly. Theimpulse coupling and plasma ignition threshold data are shown to be in good agreementwith experimental results.