In order to improve the up-conversion fluorescence intensity of rare earth ions doped micro/nano materials, a series of NaYF₄∶Yb³⁺, Tm³⁺ and NaLuF₄∶Yb³⁺, Tm³⁺ microcrystals are synthesized by oleic acid and ethanol assisted hydrothermal method. The hydrothermal products are annealed at low temperature. At the same time, the morphology of the microcrystals is fine-tuned by controlling the doping amount of Yb³⁺ to achieve spectral regulation. The results of spectral studies show that the fluorescence intensity of the samples annealed at low temperature is significantly enhanced compared with that of the parent crystals. A series of NaLuF₄∶Yb³⁺, Tm³⁺ microcrystals are synthesized by hydrothermal method using sodium citrate as surfactant, and the fluorescence intensity is further improved, and the fluorescence intensity increased with the increase of Yb³⁺ concentration. Subsequently, Ho³⁺ is introduced into the NaLuF₄∶Yb³⁺, Tm³⁺ system to regulate the fluorescence color and luminous intensity by adjusting the doping amount of Tm³⁺ and Ho³⁺. The changes of fluorescence intensity and color under different doping amounts are studied by laser spectroscopy. Taking into account the excellent fluorescence properties of NaLuF₄∶Yb³⁺, Tm³⁺, which is made for safety ink and applied to anti-counterfeiting, showing its potential application in the anti-counterfeiting field.