Acoording to the crystal symmetry, diffraction geometry and the diffraction laws, the complicated divergent beam X-ray diffraction has been studied. A method for simulating such diffraction is described. The computer generated pseudo-Kossel line patterns are exactly consistent with those recorded in experiment and the indices of all diffraction lines in the patterns can be identified. A set of standard divergent diffraction diagrams related to 〈100〉, 〈110〉 and 〈111〉oriented Si single crystals are completed successfully by computer.