According to the theory of Mie scattering, a polarization nephelometer composed of 532 nm laser as light source and charge-coupled device as detector was designed. Standard polystyrene latex (PSL) particles with particle size of 2 μm was measured, and the scattering phase function of the PSL was obtained. Compared with the theoretical scattering phase function of 2 μm spherical particles with polarization angle of 0° and 90°, the fitting degree was 87.3% and 88.4%, respectively. Chahine iteration algorithm was used to inverse the particle size of the PSL, the measured particle size was 1.94 μm, which was close to the real particle size. The results of polar nephelometer were compared with those of wide range particle size spectrometer and scanning electron microscopy. The results show that the detection precision of the device is high and not affected by subjective factors. The device is of great significance for the accurate detection of particle size, which has good application potential in related field.