Oil-dispersible β-NaLuF4:Yb3+, Er3+ colloid particles were synthesized via a facile hydrothermal method in the liquid-phase system containing ethanol-water-oleic acid-sodium oleic acid. The hexagonal phase structure of the sample was characterized by the X-ray diffraction technique. Transmission electron microscopy and high resolution transmission electron microscopy indicated that the β-NaLuF4:Yb3+, Er3+ colloid particle was crystallized in the hexagonal morphology with the size of 10nm×10nm×40nm. Upon 980 nm near-infrared irradiation, the as-prepared particles showed strong emission peak at 543nm, which corresponded to the 4S3/2-4I15/2 transition of the Er3+ ions. The double-photon emission was assigned to the emitting mechanism.