In order to implement the measurement of two-dimensional small angles, a method of modulating optical-path differences through a wedge is put forward, based on Michelson interference principle. By promoting the wedge with a voice coil motor, optical path that pass through the wedge will be changed. Then the optical-path differences on fixed points of the receiving screen will be cycle changed. Then the interference fringes will be carried out on periodical motion. Utilizing voice coil motor and right angle flexible hinge moving cycle, the relationship between the driving voltage and the displacement of wedge also has been analyzed detailedly. The experiment results show that there is a good linearity while the driving voltage is in the range 3.2v-7.5v. Modulating optical-path in this linear range, precise measurement of two-dimensional angles can be realized.