The thermal damage process of gallium arsenide (GaAs) induced by 532 nm continuous laser is presented in this work. The surface damage in the form of decomposing was detected and determined previous to the melting damage by the real-time observation of surface reflectivity. The evaporation of As induced the decrease of As content in the irradiated surface. The microscopic morphology and composition analysis of the damaged surfaces at different moments during the whole thermal process were performed with an electron probe microscope. (c) 2007 Elsevier B.V. All rights reserved.