Abstract: Using line focus laser beam of Xingguang laser facility to irradiate carbon-Aluminium target we got a X-ray point source and a line shape attenuation area of aluminium plasma. Using a fiat fleld grazing incident grating spectrometer with time resolution we measured the intensities of X-ray which emitted by carbon plasma and which passing through the Aluminum plasma,its length is 3mm. The result sbows that method can be used to measure X-ray attenuation coeficient of the plasma.