Abstract: The threshold conditions for the spallation in metal targets irradiated by a pulsed laser beam, when the induced streso wave is firstly reflected from the target's rear free surface, is proposed in this paper. The scalling law for laser flux versus streso wave intensity, the laser induced streso wave attenuation, the incident-reflective streso wave interaction, and the comparison of several spallation criteria are also discussed. The results show that for the given laser flux and target thickness, the spallation is possible only for the laser pulse duration within a certain range and, furthermore, the lowest laser flux for spallation corresponds to the optimum laser pulse duration. The method and conclusions herein are basically applicable to the flyer-impact induced spallation.