In this paper,the laser ultrasonic nondestructive testing technique is used to detect Al Cu Mg aluminum alloy.Firstly,the frequency domain attenuation coefficient of laser ultrasonic signal is extracted by Variational Modal Decomposition(VMD).Secondly,the microstructure and mechanical properties of Al Cu Mg aluminum alloy are investigated by scanning electron microscopy(SEM),electron back scattering diffraction(EBSD),tensile test and microhardness test.Then,the laser attenuation coefficient in ultrasonic domain is coupled with the microstructure and mechanical properties of Al Cu Mg aluminum alloy.The results show that the attenuation coefficient has a certain correlation with the precipitated phase content and the mechanical properties of average grain size.The laser ultrasonic detection method can identify the trend of microstructure and mechanical properties of Al Cu Mg aluminum alloy,which provides a new method for non contact,rapid and nondestructive evaluation of microstructure and mechanical properties of Al Cu Mg aluminum alloy.