The polarization pinhole interferomenter is a new practical instrument. It synthesizes the techniques of pinhole diffraction, common light path and polarization technique in its design. It has many advantages, such as the fringe contrast adjustable, nondestructive testing, and strong anti-interference ability. The instrument can be used extensively in various optical element testing and their glue layer testing. The accurace of the fringe pattern analysis is controlled by the fringe sample point numbers.