A high-through put μ-EDXRF instrument named NX-mapping with polycapillary optics and 4~6 SDD detectors placed symmetrically around the emitted focal spot was developed. We designed the software to control the X-ray source, multiple detectors, and high-precision stage and carried out the work of data collection, signal synchronization and result in analysis simultaneously. Due to the use of multiple detectors, the intensity of this XRF instrument was improved several times, and the RSD was reduced to 40% hasn’t deteriorated due to the differences between several detectors and the moving stage.There is no significant difference between the RSD of scanning a uniform sample with 2 mm×2 mm square 400 pixels and the fixed-point test, indicating that the motion mechanism and control algorithm performed well. The fluorescent knife-edge test was carried out forthe effective focal size testing of NX-mapping. The minimum effective focal size of Fe, Ni and Mo elements are 52.4, 49.3 and 39.03 μm. The law that each element’s effective focal spot size decreases with the increase of atomic number is summarized, which is consistent with the design principle of polycapillary optics.It is also found that the effective size of the focal spot of each element is sensitive to the change of height at the minimum value. Therefore, it is recommended to keep the surface of the sample flat in order to obtain uniform and clear images.Finally, the characteristic intensity of elements Ni, Ta, W and Re of a single crystal superalloy sample were scanned and analyzed by NX-mapping. The images of the dendritic structure can be distinguished, and the intensity of the Ni∶Ka characteristic line was up to 220 kcps, which was significantly higher than that of the ordinary XRF test. The NX-mapping μ-EDXRF instrument with multiple detectors, which provide high signal intensity, good test precision and shorter test time,can meet the requirements of high-through put testing.