Abstract: OBJECTIVE To establish a method for determination of the particle size and particle size distribution of paracetamol by laser diffraction method. METHODS The Malvern Mastersizer 2000 laser size analyzer was used to test particle size and particle size distribution of paracetamol by the wet measurement. The n-hexane containing 0.1% of soybean lecithin was used for the dispersion, the sample refractive index was 1.70, the sample absorption rate was 0.1 and the shading rate was 10%-20%. Determine the samples after sonicating for 20s at the pump speed of 2000 r·min^-1. RESULTS A variety of paracetamol products could be analyzed by laser diffraction method. The D4,3 could show the size difference between different products. The RSD of d(0.5) was less than 3%, and the RSDs of d(0.1) and d(0.9) were both less than 5%. The method had good repeatability. CONCLUSION The method is fast, simple, accurate and producible, which is suitable for the particle size control of paracetamol.