Based on the unique advantages of synchrotron radiation X-ray with high resolution and collimation，and the advantage of nondestructive observation of computed-tomography technique，synchrotron radiation computed tomography technique is widely used in many fields. In this paper，the errors caused by light source such as unevenness，supersaturation and super penetration are studied for synchrotron radiation computed tomography technique，and its three basic error forms are given. Numerical simulation results confirm this analysis.