Abstract: A MachZehnder interferometer was developed for studying the plasma implosion in zpinch. The experiment with the interferometer was conducted on a small gaspuff Zpinch device and clear interferograms were obtained. By counting the fringe shift on the interferograms, the average electron densities of plasma well before its final pinch were calculated to be on the order of 1017~1018cm-3. If a beam splitter with time delay is inserted between the YAG laser and the MZ interferometer, a multiframe interferometer could be constructed, which is capable of taking several pictures within a single shot of Zpinch discharge.