Abstract: This paper presents a new way to measure the characteristic parameter of the phase shifting controller made of fiber with PZT by phase shifting. The method is phase shifting with any four steps in a facultative interval,and in combination with grouping disposal the parameter is got. This way can also be used to self-verify by the controller.

Key words: the phase shifting controller made of fiber with PZT； phase shifting technic； interference system of M-Z optic fiber；