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We accomplish a laboratory facility for producing a femtosecond XUV coherent monochromatic radiation with a broad tunable spectral range of 20 eV-75 eV.It is based on spectral selected single-order harmonics from intense laser driven high harmonic generation in gas phase.The time preserving for the selected harmonic radiation is achieved by a CzemyTumer type monochromator designed with a conical diffraction grating mount for minimizing the time broadening caused by grating diffraction and keeping a relatively high diffraction efficiency.Our measurement shows that the photon flux of the 23-order harmonic (H23) centered at 35.7 eV is 1 × 109 photons/s approximately with a resolving power E/AE ≈ 36.This source provides an ultrashort tunable monochromatic XUV beam for ultrafast studies of electronic and structural dynamics in a large variety of matters.