Abstract: Electrostatic precipitator (ESP), which separates particules from air stream by means of electrostatic field to reach the goal of air cleaning, has been successfully applied in highway tunnels in Europe, Japan and other developed countries. However it is still in an exploratory stage in China, and there are few industry norms and design standards specified for road tunnels. In this paper a set of ESP system was designed and tested in an operating road tunnel, with the research results show that the concentrations of particulates were largely reduced and the air quality was significantly improved thanks to the ESP system. It contributes to getting the experience in developing,designing and operating of the ESP system, and the theoretical basis for the application in domestic highway tunnels and underground space.