Abstract: The stress histories of aluminum plates with different thicknesses induced by a Q -swiched Nd -glass laser beam of pulse duration 70ns and flux of 10⁷ ~ 10⁸W/cm² measured with a piezoelectric transducer of x -cut quartzcrystul of 10mm in diamerer and 1.2mm or 2mm in thickness. The spot diameter on the samples front was 10mm. The experimental results show that the peak stress σ_max is proportional approximately to the square of laser bear flux I² for I=（3 ⁷）J/cm². The scaling of σ_max vs the propagation distance x seems tobe σ_max∝x^{-（1.02～1.29）}. An analytical calculation identifies the hot -elastic mechanism of the laser induced stress wave in the aluminum targets herein.