Laser crystals of LiYF4 (LYF) singly doped with Er3+ in 2.0% and co-doped with Er3+/yb3+ in about 2.0%/1.0% molar fraction in the raw composition are grown by a vertical Bridgrnan method.X-ray diffraction (XRD),absorption spectra,fluorescence spectra and decay curves are measured to investigate the structural and luminescent properties of the crystals.Compared with the Er3+ singly doped sample,obviously enhanced emission at 1.5 μm wavelength and green and red up-conversion emissions from Er3+/yb3+ co-doped crystal are observed under the excitation of 980 nm laser diode.Meanwhile,the emission at 2.7μm wavelength from Er3+ singly doped crystal is reduced.The fluorescence decay time ranging from 18.60 ms for Er3+ singly doped crystal to 23.01 ms for Er3+/yb3+ co-doped crystal depends on the ionic concentration.The luminescent mechanisms for the Er3+/yb3+ co-doped crystals are analyzed,and the possible energy transfer processes from Yb3+ to Er3+ are proposed.