Abstract: This paper is concerned with the techniques of masking and removing layers of silicon wafers coupled with neutron activation analysis, and the method of the determination of the depth profile of gold in silicon wafers. Reliable and convenient masking can be made by means of a homemade mould which has good corrosion resistance. The mould is particularly suitable for radioactive samples. The effects of composition of etchant, etching temperature and etching time on etching rate are also investigated. By means of this method, each removed thin layer can reach 5-20 μm in thickness. The total deviation of removed layer thickness is about±3%.