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Li ions affect the upconversion efficiency by changing the local crystal field of the luminescent center. Herein, in order to improve the upconversion efficiency of NaYF4:Yb3 /Eu3 , a series of NaYF4:Yb3 /Eu3 micro-particles with different Li doping concentrations were synthesized by the hydrothermal synthesis method, respectively. Firstly, the structure and morphology of NaYF4:Yb3 /Eu3 upconversion micro-particles (UCMPs) with different doping concentrations were analyzed by X-ray diffraction and a scanning electron microscope (SEM). SEM results show that the UCMPs are not only highly crystallized, but also have hexagons with different Li concentrations of NaYF4:Yb3 /Eu3 . X-ray diffraction shows that the crystal field around Eu3 changes with the increase of Li concentration. Then, the fluorescence spectrum of NaYF4:Yb3 /Eu3 was studied under the irradiation of a 980 nm laser. The results show that the fluorescence intensity of NaYF4:Yb3 /Eu3 with 2% Li is the strongest, which is twice the intensity of NaYF4:Yb3 /Eu3 without Li . Finally, the fluorescence imaging analysis of NaYF4:Yb3 /Eu3 with 2% Li concentration was carried out. The UCMPs are used to screen printing to evaluate the imaging effect on different sample surfaces. The results show NaYF4:Yb3 /Eu3 (with 2% Li ) has great application prospects in anti-counterfeiting recognition.