Crystal growth of KLu2F7 nanocrystals is investigated by dosage-and time-dependent analysis. XRD patterns reveal the phase transition along with the dosage of fluorine source and reaction times, where the cubic-phase KLu3F10 turns into orthorhombic KLu2F7. TEM images show that the dimensions of as-prepared samples are below a hundred nanometers, with different shapes from hexagonal plate to hexagonal rod. The upconversion properties of the as-prepared samples are investigated. It is found that the upconversion emission is lowered as the shape of the samples varies. Moreover, the orthorhombic KLu2F7: Yb, Er nanocrystals present more enormous upconversion luminescence than the cubic counterparts. In a word, the orthorhombic nanocrystals are found to be good candidate for upconversion luminescence and of great importance for potential applications in solar cells, multicolor display and bioimaging. (C) 2018 Elsevier B.V. All rights reserved.