An experimental system of interferometric particle imaging with opposition of two laser- sheets illumination at scattering angle q=90° is presented. The center of particle imaged can be extracted through the template matching correlation operation between the particle focused images and the particle mask image. The focused image of each particle can then be achieved by using the center coordinate, the shape and size of the particle mask image. The spacing of the doublet image of the individual particle is evaluated by the auto-correlation method and Gaussian interpolation, and sub-pixel accuracy of the glare point separation extraction is acquired. Then particle diameter is calculated. The result is that for particle diameter (46.54 ± 0.50) μm, the relative error is 3.42% for the standard particles with diameter of 45 μm. The research results show that the experimental system and algorithm presented in this paper are feasible.