MEMS (Micro-Electro-Mechanical Systems) and MOEMS (Micro-Opto-Electro-Mechanical Systems) are devices comprised of integrated mechanical,electrical and optical components,manufactured using techniques similar to those of integrated circuits.As in semiconductor manufacturing,quality control is the key to successful products-so much so that 50-80% of the cost of a MEMS device is incurred in final packaging and test. Interferometer,which combines high speed,accuracy,resolution and flexibility,has proven successful for measuring nano-surface features of unpackaged MEMS devices.With the further productization of MEMS technology,however,devices also need to be tested in their final,packaged state,typically beneath a protective,transparent cover.In this paper,we introduce the application of interferometer in nano-surface measurement.First of all,nanotechnology and principle of interferometer are briefly described.Second,both dimension and surface measurement are given out.Third,typical techniques used in the interferometer are discussed.Fourth,variously industrial applications are listed.Finally,taking optical testing as an example of nano-surface measurement,both worldwide and China market are analyzed.