This paper briefly introduces the sagittal focusing and monochromatizing principle about the beam between 5～25keV. Sagittal focusing monochromatizing principle about beam is based on Bragg law (2dsinθ=nλ) and the monochromic beam is obtained by changing Bragg angle θ. According to the relation between θ and sagittal focusing radius R, the monochromator makes the monochromic and sagittal focusing beam realize. Then the paper explains the principle about crystal bending based on flexible hinge, the control about anticlastic distortion, the structure ensuring the fixing height between the input and output beam and the result on the finite element model about the surface of bending crystal. Finally the paper gives the result experiment.