Abstract: In this paper, the physical process of producing X-rays in the X-ray source used in cone-beam industrial CT system was simulated by Monte Carlo method. The X-ray spectrums with and with no 2 mm iron as filter layers were obtained, respectively. In addition, the angular distribution of the outgoing X-ray flux under different target angles was calculated. Then, the intensity distribution of the X-rays which passed through the object under test was simulated. We obtain the distribution of SPR value and the distribution of X-ray intensity in different positions of the detector plane in different conditions, which are in the same distance between the ray source and the detector and passing through the object of the same diameter. Besides, we also obtain the flux spectrum distribution in the centre of detector and the spatial distribution of the X-ray intensity in some special position. The simulation results in this paper can provide some help and basis for the scatter correction and beam hardening correction in the process of image reconstruction and help to determine the minimum sensitivity of the detector, and provide a reference for the shielding system design.