Abstract: Purpose Improvement of CT contrast resolution since 1973, medical CT has gained great progress to improve its spatial and temporal resolutions. Recently, the spatial resolution of the fifth generation of medical CT of high resolution has reached 0.35mm. The temporal resolution of the high speed electronic beam CT has reached 20ms per frame. But the improvement of the CT contrast (density) resolution is not significant. Since the CT contrast (density) resolution is closely correlated with the gray grade of CT image and is very important to the distinction of CT images, so it is necessary to investigate how to improve the contrast resolution of the CT images. Method and Conclusion The principle and mechanism of the dual photons absorption method to improve the CT contrast (density) resolution were suggested and analyzed. The feasibility of this method in practical application was also discussed.