Series of Tm3+/Yb3+ co-doped GdF3 powders were synthesized through aneasy and mild hydrothermal method. The phase and purity of powders werecharacterized by powder X-ray diffraction (XRD) (Rigaku RU-200b). Themorphologies of the samples were characterized by field emission scanningelectron microscopy (FE-SEM) (Hitachi S-4800). The ultraviolet (UV) up-conversion(UC)emission spectra were recorded by a fluorescence spectrophotometer (HitachiF-4500) with a 980 nm semiconductor continuous wave laser diode as the excitationsource. And the luminescent dynamics was measured by excitation with 980 nm usingan optical parameter oscillator (OPO) laser pumped by a pulsed Nd∶YAG laser witha pulse duration of 10 ns, repetition frequency of 10 Hz, and the signal wasrecorded by using a monochromator and an oscillograph. Under 980 nm excitation,Gd3+, acting as a kind of host ion in the studied system, and its UV UC emissionswere observed and studied. The luminescent dynamics of the characteristicemission of Gd3+ (311.6 nm, 6P7/2→8S7/2) was explored and studied. Theluminescent dynamics analysis results indicated that, on UV UC emissions of Gd3+,Yb3+ ions served as primary sensitizer ions successively transferring energy toTm3+ to populate the 3P2 level. Then, Tm3+ ions served as secondary sensitizerions transferring energy to populate the multiple 6IJ states of Gd3+ 3P2→3H6(Tm3+): 8S7/2→6IJ (Gd3+). Further, 6DJ levels were populated through otherenergy transfer processes between Gd3+ and Yb3+ or Tm3+. Finally, UV UC emissionsfrom the excited 6D9/2, 6IJ, 6P5/2, and 6P7/2 states to the ground state 8S7/2were observed. Meanwhile, Tm3+ acted as activator in its own UC emissions, andthe article did not put emphasis on those except the 3P2 and 1I6 levels to theground state 3H6 transitions. Especially, the dependences of UV UC emissions ofGd3+ on the Yb3+ concentrations, the Tm3+ concentrations, the annealingtemperatures, and the excitation power densities of the 980 nm semiconductorcontinuous wave laser diode were studied, too.Luminescent dynamics(2009GQW0010)和江西省教育厅科技计划项目(GJJ10203)资助