This work designs and implements an inexpensive and simple double-crystal monochromator, which yields a high performance at a bending magnet x-ray beamline. A primary feature of the proposed monochromator is that the offset between the incident and monochromatic exit of the x-ray beam can be adjusted to cover a wide energy range with a short X–YX–Y traveling stroke. Such a short range of X–YX–Y strokes can reduce the monochromator’s overall size and, also, increase the stability of motions. Meanwhile, in this monochromator, instead of using a complicated hardware linkage mechanism, a software program is developed to effectively control the X–YX–Y stage for positioning the second crystal in a fixed exit configuration, alleviating mechanic motion errors to maintain the parallelism of the two crystals. The entire software control mechanical linkage offers a relatively inexpensive and simple assembly monochromator that is more flexible than the commercially available one.