Electrospun nanobelts were prepared from lanthanum oxybromide doped with trivalent erbium ions (La2O3:Er3+), then up-conversion nanobelts were successfully synthesized from these by bromination with ammonium bromide (NH4Br) powder as bromine source and use of a double-crucible method. The products were characterized in detail by x-ray diffractometry, scanning electron microscopy, energy dispersion spectroscopy, and fluorescence spectroscopy. The results indicated the LaOBr:Er3+ nanobelts were tetragonal in structure with the space group P4/nmm. The width and the thickness of LaOBr:Er3+ nanobelts were 3.06 +/- A 0.42 mu m and 290 nm, respectively. On excitation with a 980-nm diode laser, LaOBr:Er3+ the nanobelts emitted strong green and red up-conversion emission centered at 522 nm, 541 nm, and 667 nm. The green and red emission was assigned to the energy level transitions H-2(11/2) -> I-4(15/2), S-4(3/2) -> I-4(15/2), and F-4(9/2) -> I-4 (l5/2) of the erbium ions (Er3+). A mechanism of formation LaOBr:Er3+ up-conversion luminescence nanobelts is proposed. This bromination technique not only results in preservation of the morphology of precursor rare earth oxides, it can also be used to fabricate other pure-phase rare earth oxybromide luminescence nanomaterials at relatively low calcination temperatures.