A method using white-light Michelson interferometer and polarization interferometry system for measuring the retardation of wave plates (including the order of retardation) is presented. The linear polarized white-light passes through the test wave plate which introduces retardation between the o-beam and e-beam, and then they are divided by a beam splitter and reflected by two plane mirrors of the Michelson interferometer respectively. Finally three white-light interference packets are formed. For a multiple-order wave plate, the interference packets will be separated absolutely, and according to the optical path between the center packet and one of the side packets, the retardation of multiple-order wave plates can be obtained. The retardation of a lower-order wave plate and the stress of a optical glass can be calculated by using the phase variation after inserting it behind the multiple-order wave plate. The retardations of a multiple-order and zero-order wave plate are measured in experiments, whose results coincide with the ones obtained by spectroscopic method.