Abstract: The double crystal diffraction structure based on Bragg diffraction is the core component of the monochromator commonly used in synchrotron radiation beamlines and monochromatic X-ray radiation devices. The stability of the monochromatic X-ray generated by the T-structure double crystal monochromator was investigated. In addition, inspired by the Channel-cut monochromator structure, a new double crystal monochromator structure was designed, and stability of the diffraction-generated monochromatic X-ray was tested. The experimental results show that the stability of the monochromatic X-ray flux generated by the T-structure double crystal monochromator is poor due to its structural defects, while the stability of the monochromatic X-ray flux generated by the new double crystal monochromator structure is better than 1.0%, and the energy range and dose rate of the monochromatic X-ray are significantly improved.