As common-path interferometers, shearography (shear interferometer) has been widely used in many fields. It has some special advantages as well as some disadvantages. This leads to the result that it can only be used in some special conditions for some special uses. Int his paper, both the advantages and the disadvantages are discussed. Some new progress, such as the phase-shift in shearography, two-dimensional shearography and the phot-carrier in shearography, are proposed. All of these new progress are developed in the aim of extending the application fields, improving the processing accuracy and realizing automatic measurement.