Abstract: Lapping quartz glass is the former process of its ultra-smooth polishing process, which greatly affects its machining efficiency and final surface quality.To meet the hard and brittle characteristics of the quartz glass, a new fixed diamond aggregation pad (FDAP) was employed to study the high efficiency and low damage lapping process.The effect of original abrasive size, secondary abrasive size, applied load and slurry flow rate on the lapping performance was explored.After comprehensive optimization, the process parameters with high processing efficiency and excellent surface quality were obtained. The results show that the FDAP exhibits an excellent lapping performance.When the original abrasive size and secondary abrasive grain size are 1.0~2.0 μm and 20~25 μm respectively, with load 14 kPa and slurry flow rate 60 mL/min, the material removal rate of quartz glass reaches 2.64 μm/min and average surface roughness R_a is 54.2 nm.