Abstract: When the fluorescent samples were analyzed using a windowed X-ray energy dispersive spectrometer (EDS) equipped with a scanning electron microscope, due to the excitation of the electron beam, the stimulated fluorescence by sample stimulation will seriously interfere with the analysis of the characteristic X-rays by the EDS energy spectroscopy probe, which leads to qualitative and quantitative difficulties. The new windowless EDS combined with the method of single particle small region acquisition can successfully achieve normal EDS spectral analysis of fluorescent samples because of its excellent low-energy-end signal acquisition and analysis capability. Without the adsorption of the traditional ultra-thin window, the windowless EDS can analyze lithium metal. By optimizing the accelerating voltage and the protective effect of the passivation film on the sample surface, the interference of background noise and sample contamination were overcome, and the detection of elemental lithium was successfully realized.