Lots of research work on the X-ray pulsar navigation detector has been carried out, but the rigorous quantitative calibration results of these detectors have never been given out. In order to further promote the research process in X-ray pulsar navigation field, a kind of high-precision X-ray source which could be tunable in energy distribution and photon flux is necessary. A new method has been proposed to generate such an X-ray source, in which a conventional X-ray tube which is called the original level tube is used to excite a special fluorescence target to generate fluorescence X-ray source. Firstly, the primary experiment system is built, with which the intensity of the fluorescence X-ray source is measured in atmospheric environment. The result indicates that the fluorescence X-ray source can be implemented in vacuum system to calibrate the detectors. Then an integral fluorescence X-ray source is fabricated which can be used in vacuum system and its intensity is measured under the condition of Dx=300 cm and Ia=200 μA. The photo fluxes are obtained to be 19.57 phs/s at 4.51 keV, 25.22 phs/s at 5.41 keV, and 33.27 phs/s at 8.05 keV. These data demonstrate the correctness of our method and that this new fluorescence X-ray source can be used to calibrate the x-ray pulsar navigation detector.