Indium tin oxide (ITO) thin film with SiO 2 protective upper layer prepared by electron beam evaporation was annealed in air up to 300qC. Evolution of transmittance, resistance and surface morphology of this SiO 2 /ITO coating was studied. Transmittance in visible and n ear-infrared range both increased while absorption edge exhibited red shift after annealing. Resistance increased monotonously with rising annealing temperature, yet increments became smaller at temperatures above 270qC. Micron-defects were observed on the surface of SiO 2 /ITO coating after annealing. Enhancement of crystallinity of ITO layer at high temperatures was thought to be responsible for these morphology and resistance evolutions. Keywords: ITO, air-annealing, surface morphology, crystallinity 1. INTRODUCTION Indium tin oxide (ITO) films were widely applied in flat panel display 1 , solar cells 2 , lighting diodes 3 , electromagnetic shields 4 and antifogging windows because of their excellent conductivity (>10