Experiment research on the factors which affect the wet etching quality of ST cut quartz is performed, and the results are discussed in depth. In our experiments, double side polished ST cut quartz, Cr/Au double films, mixtures of hydrofluoric acid (HF) and ammonium fluoride (NH4F), are selected as etch wafer, etch mask and etchants, respectively. The effects of the process parameters including wafer cleaning, composition proportion of etchants and etching temperature on the etching quality of the substrate surface have been investigated. The optimal process parameters are acquired and the crystal surface meeting the requirements is fabricated under moderate etching rate of 0.7 μm/min.