Abstract: Xray imaging system based on spherically bent crystal is an important diagnostic technique for inertial confinement fusion (ICF). To testify the performance of the imaging system and optimize the structure of imaging system, the backlighting imaging system was studied by the ray tracing software SHADOW. Through the analysis for the system parametes, such as the position of object, the radius and Bragg angle, the results showed that for the spherical surface crystal back light imaging systems with Bragg angle of 57 and 65 ,when the object thickness or object laying aside error was a=1 mm, the crystal bevelling radius error was R=3 mm, and the Bragg angle error =0.1 mrad, the relative magnification of the 2 imaging systems simulated on the meridian plane and the sagittal plane through light tracing ,tailled with the computation result by relative magnification formula comparison.It is implied that the parameters have a little influence on the relative magnification of the imaging system, and the performance of imaging system is stable and reliable.