In this paper, large and transparent K2Al2B2O7 (KABO) crystals were grown using NaF as a flux in a non-oxygen atmosphere for the first time. Through optimization of the growth condition, bulk KABO crystal has been obtained with good quality. The transmittance spectrum shows that the abnormal UV absorption from 200 to 300 nm of KABO crystals could be effectively eliminated by this new method. The non-UV absorption KABO crystal is promising for the application of fourth harmonic generation of Nd:YAG lasers. A 280 mW average output power was obtained through fourth harmonic generation of Nd:YAG laser with 10 kHz, 10 ns pulse and a 8.85-mm-thick KABO crystal. The conversion efficiency up to 33.4% of second harmonic generation from 532 to 266 nm has also been achieved with a 25 ps, 10 Hz laser system and the same crystal. To our knowledge, this is the highest result at present. (C) 2010 Elsevier B.V. All rights reserved.