In order to improve the accuracy of non-contact imaging measurement, it is rather essential for people to identify the radiation calibration of charge-coupled device (CCD). This article explains the theory and necessity of radiation calibration in the field of non-contact imaging measurement through an experiment in which the quantitative relationship between the radiation intensity of illumination at the surface of CCD and the digital of gray value is built, resulting in the penalty function of the camera. Consequently, the radiation calibration of CCD has been accomplished within the limits of the prescriptive uncertainty.