A method for the measurement of particle size with interferometric particle imaging (IPI) technique is studied. The interferometric pattern of the scattering light of particle is formed in the defocused image plane and the center of the fringe pattern is extracted by the wavelet transform and template matching method. The number of fringe/fringe spacing of the interferogram by Fourier transform and the modified Rife algorithm is obtained, and particle size with subpixel accuracy is calculated. The experiment is conducted for standard particles of diameter 51.1 μm. The particle diameter is measured of (49.79±0.41) μm with the absolute error of 1.31 μm. And this technique is applied to alcohol spray measuring. The particle size distribution, mean particle diameter and Sauter mean diameter (SMD) of the spray field with different measuring locations along x-axis and y-axis are also given.