Abstract: The surface quality of Pyrex glass（Corning 7740）is crucial for the optical performance of MEMS devices.In this paper,a kind of deep wet etching process of pyrex glass using a muhilayer etching mask of TiW/Au in combination with AZA620 thick photoresist is experimentally studied.To obtain high quality etching glass surface,the main factors causing surface defects and roughness are analyzed. The etched results show that the muhilayer mask used is more effective to eliminate the pinholes generated during deep etching,and the high quality surface is obtained by using hydrochloric acid as etching additive into hydrofluoric acid solution.The roughness of etched glass surface can be reduced from 14.1 nm to 2.3nm（RMS）,while HF（40%）and HC1（37%）solutions are blended with a volumetric ratio 10:1. No pinholes have been observed on the glass surface after the developed etching process of a depth of 150μm.Since then,a novel fabrication process is accomplished to bond Cr/Au wires and alignment signs for MEMS devices.