Particle size measurement technology is widely used in many fields such as energy, materials, medicine, chemical industry, metallurgy, electronics, machinery, light industry, construction, etc., and has a very important meaning for improving product quality, increasing production efficiency, reducing energy consumption, realizing precision medicine, monitoring environmental pollution, etc. The particle size measurement method based on the optical principle has the advantages of fast response speed, and the particle size measurement range can reach nanometer level. However, there are still some problems in practical applications and need to be continuously improved. Three types of particle size measurement methods based on optical principles: Microscopy, light scattering, and laser imaging were summarized in this paper, including the measurement principles, measurement ranges, advantages and disadvantages, and application areas of various methods. On this basis, the prospects for the research of particle size measurement were prospected.