The upconversion (UC) emission properties of rare-earth ions are not only dependent on the host materials, but also relate to the excitation conditions. In this work, taking the Ho³⁺ ions for example, upconversion emission properties are studied in two NaYF₄ and LiYF₄ fluoride microcrystals through changing excitation conditions, namely the excitation power and the sample environment. The NaYF₄:20%Yb³⁺/2%Ho³⁺ and NaYF₄:20%Yb³⁺/2%Ho³⁺ microcrystal are synthesized by the hydrothermal method. The typical X-ray diffraction patterns of NaYF₄:20%Yb³⁺/2%Ho³⁺ and LiYF₄:20%Yb³⁺/2%Ho³⁺ microcrystal indicate that the prepared samples possess pure hexagonal phase NaYF₄ structure and the pure tetragonal phase LiYF₄ structure with high crystallinity, respectively. Most of NaYF₄:20%Yb³⁺/2%Ho³⁺ microcrystals show uniform and regular rod shape with diameter and length of approximately 3 μm and 10 μm, respectively. Few rods with a length of approximately 5 μm are also observed. The LiYF₄:20%Yb³⁺/2%Ho³⁺ microcrystals are all octahedral in shape with a smooth surface, the average size is around 10 μm. The spectral peculiarities of Ho³⁺ are investigated by using confocal microscopy equipment under near infrared 980 nm excitation. Beautiful patterns with different upconversion emissions of Ho³⁺ are discovered in single NaYF₄ and LiYF₄ microcrystal. As the excitation power increases, the upconversion emission of Ho³⁺ turns from green to pink in single NaYF₄ microrods due to the cross-relaxation between Ho³⁺ and the energy back transfer from Ho³⁺ to Yb³⁺. However, in single LiYF₄:Ho³⁺ microcrystal no similar phenomenon is observed. Nevertheless, when the powder of NaYF₄ and LiYF₄ microcrystals are excited by a 980 nm laser, increasing the power can turn the output colours of Ho³⁺ all green. Because particles outside the laser radiation are not directly covered by the laser, most of them are excited by the scattered light from the laser, and the actual excitation energy is low compared with at the center position. This result can be proved in the single NaYF₄ and LiYF₄ microcrystal under low excitation power. Thus, the results indicate that UC emission of rare-earth ions is controlled by changing the excitation condition. Using the new testing methods we can not only observe more interesting spectral phenomena, but also find a new way to further study its luminescence mechanism.