Abstract: In this paper, the WESP fine particle strengthening removal mechanism is analyzed for the first time from the aspects of strengthened charging and promoted fine particle coalescence. Then through further investigation and on-site measurement, the PM emission characteristics of WESP are studied comprehensively. The inlet and outlet particle size distribution, total dust concentration, PM₁₀/PM_2.5 concentration and SO₃ concentration of WESP were measured by virtue of ELPI, filter cartridge, ELPI/PM-10 or DGI and condensation method, respectively. Based on the statistical analysis of the research and measured data, it is shown that PM₁₀ is divided into 12 levels ranged from 0.03 μm to 10 μm by using ELPI and dust particles in each level are removed significantly using WESP with the removal efficiency of both number concentration and mass concentration exceeding 40%, and the maximum even reaching more than 90%. The outlet dust concentration of WESP is between 0.43 mg/m³ and 12.5 mg/m³, most of which is lower than 5 mg/m³. Moreover, dust removal efficiency is above 70%, with the maximum over 90%. The outlet PM_2.5 concentrations of WESP are limited in the range between 0.35 mg/m³ and 1.59 mg/m³ while most of them are lower than 1 mg/m³ and PM_2.5 removal efficiency is above 60%, with the maximum more than 90%. The outlet SO₃ concentration of WESP is within the range between 0.10 mg/m³ and 3.21 mg/m³. SO₃ removal efficiency is achieved above 60% with the maximum more than 90%. The outlet CEMS data for three months of continuous operation of WESP of a 350 MW unit was studied and the result showed that hourly concentration control rate reached 100%. Therefore long term stable operation of the system is realized.