In this study, we have obtained the distribution of Cherenkov light generated by X-rays (10MV), and investigated the relationship between Cherenkov light and the absorbed dose. Furthermore, we have examined whether we could calculate Cherenkov light by EGS(electron-gammashower). In order to measure the light the films were stuck to the collimator that was set at the side of the aquarium irradiated by X-rays, when the turntable was rotated at the step of 15 degrees. Secondly, the film densities of photograph were changed to the light exposure. Moreover, we obtained the CT image based on Cherenkov light. Its image is regarded as the distribution of Cherenkov light. In the comparison between the distribution of Cherenkov light obtained in the experiment and that of the absorbed dose calculated by EGS, they were approximately equal to each other. However, the amount of the relative light outside the irradiation field is greater than that of the relative absorbed dose calculated by EGS. It could be due to the aperture size of the collimator for the light. The distribution of Cherenkov light obtained in the experiment and that calculated by EGS were the almost same. It seems that the light can be calculated by EGS. In conclusion, Cherenkov light was concerned with the absorbed dose. Thus, it may be possible to calculate the absorbed dose by measuring Cherenkov light.