Abstract: This paper introduces the principle of the computer radiography technology and intensifying screen. Using 9 MeV X-ray accelerator system, iCR3600+ and CR UR-1 IP board, etc., the transillumination of steel plate with different thicknesses shows the imaging sensitization effect of the intensifying screen to IP board. Corresponding thicknesses of intensifying screen resulting in the highest sensitivity for steel plate of various thicknesses were obtained, which might provide useful reference for engineering applications.