A method of fast scanning X-ray microprobe fluorescence imaging, on-the-fly scan, has been recently accomplished in BL15U1 hard X-ray micro-focus beamline of Shanghai Synchrotron Radiation Facility, based on the software platform of EPICS; the high technology of precise motion control, the X-ray flux detection and the X-ray fluorescence spectrum detection are integrated into this system. By the method of X-ray microprobe fluorescence imaging, the images of standard nickel mask and the elemental distribution of copper, zinc, kalium and iron in specimen of mouse spleen are obtained. The results demonstrate that this method not only enhances the efficiency on a large scale, but also achieves high quality fluorescence mapping.