A series of ultra-precision grinding experiments were carried out on transparent AlON ceramic. The grinding parameters (wheel speed, workpiece speed, feedrate and depth of grinding) were optimized by studying the influence of process parameters on surface quality. Comprehensive consideration of surface quality and machining efficiency, the grinding process parameters selected for finishing are as bellow: the wheel speed is 6000rpm, the workpiece speed is 39rpm, the feedrate is 5mm/min and the depth of grinding is 3μm. A grinding verification experiment was carried out after optimization. According to the optimized process parameters, the AlON optical window (the diameter is 120mm, the length-diameter ratio is 1.08, the thickness is 3mm) was processed by ultra-precision grinding. The form accuracy, surface roughness and infrared transmittance of the AlON optical window were tested and discussed.