The invention discloses an ytterbium/thulium-ion-codoped hexagonal-phase sodium yttrium fluoride microcrystal with red-light oriented emission performance. The crystal is synthesized in an alkaline environment by using sodium fluoride as a fluorine source. The synthesis method is simple and controllable, and has the advantages of mild reaction conditions and no need of modification as compared with the thermal decomposition process. The prepared ytterbium/thulium-ion-codoped hexagonal-phase sodium yttrium fluoride microcrystal has the advantages of favorable crystallinity, favorable dispersity, uniform size and high water solubility, and has unique light emission characteristics. When exciting light performs excitation downwards along the central position of any one corner or cambered side or the central shaft of a single microcrystal, or along the central shaft or an adjacent corner of any one of a plurality of microcrystals, red-light oriented emission can be implemented. By using such unique light emission characteristics, the material is applicable to laser devices, and can implement monochromatic-light oriented emission without band-limited filter plates. The material is also applicable to biological imaging, and can accurately control the position of the exciting light. The material can also be used as a wave guide modulator to be used in research and development of novel photoelectric devices.