Abstract: Michelson interferometer experiment for extended lights was performed. When the extended light was incident upon the Michelson interferometer, and the transparent optical layers were added into each interferential arm, the dislocation phenomena of the peak of the time and space coherent envelop for exit light was observed under two conditions. It is proved that the optical wave coherent characteristic in the interference field can be destroyed by adding optical layers in the different interferential arm, which results in lead or lag for the time and the spatial coherence. Based on this effect, the measurement of the thickness and refractive index of optical elements can be implemented experimentally with two incident beams. The relevant calculation formulas are given.