The GdAl3(BO3)(4):Tm3+ crystal with size up to 15 mm x 15 mm x 25 mm was grown from the K2O3-MoO3-B2O3 solvent system by the top seed solution growth (TSSG) method. The absorption spectrum was measured and its absorption peaks were assigned. The emission spectrum ranging from 500 to 1800nm was obtained from 468nm wavelength pumping. The absorption cross section sigma(a). at 800 nm was determined. (C) 2004 Elsevier B.V. All rights reserved.