The plasma of lithium triborate (LiB3O5, LBO) crystal produced by the 1.06 mum Nd:YAG laser ablation in vacuum and in air is studied spectroscopically in time-integrated manner. Electron density (N-c) and temperature (T-c) of the plasma in vacuum are determined by using Stark-broadened line width of Li atoms and the relative emission line intensities of successive ionized stages of B atoms, respectively. The dependence of electron density, electron temperature, and spectra properties on distance from the target surface and laser irradiance is investigated. By comparing the optical emission spectra (OES) in vacuum with those in air, the effects of background gas are discussed. The validity of local thermal equilibrium assumption is testified. (C) 2003 Elsevier Science B.V. All rights reserved.