Yb3+/Ln(3+) co-doped LiYF4 and LiLuF4 microcrystals (MCs) are synthesized by a facile hydrothermal method. The upconversion (UC) luminescence properties of single LiYF4 and LiLuE4:Yb3+/Ln(3+) MC are studied by a confocal microscopy setup under NIR 980 nm laser excitation. The single LiLuF4 MC displays stronger UC emission intensity than that of single LiYF4 MC, which is due to the varied site symmetry of the crystal field. The possible UC mechanism, the influence of surface properties and excitation positions on the UC luminescence emission are also investigated. Investigating the luminescence properties of a single particle can effectively avoid environmental influence, achieve selective targeting excitation, and provide precise information for studying the luminescence mechanism of Ln(3+) ions. (C) 2017 Published by Elsevier