In this study, we developed a separated two-stage electrostatic precipitator applicable in a subway air conditioning system. We studied the characteristics of collection efficiency of 0.3 μm particle and ozone generation at different charger sizes and gaps of collector plates. Also, we compared the performance of the two-stage ESP to the MERV 10 filter with the removal efficiency of 10% used in actual subway air conditioning system. The maximum collection efficiency of 0.3 μm particle was 93% at A charger (600 mm⨯250 mm⨯600 mm) and 84% at B charger (330 mm ⨯280 mm⨯330 mm). Especially, with voltages applied to chargers with collection efficiency of about 80% or more, the ozone concentration of two different chargers was 5 ppb to 35 ppb. Finally, the filter quality of the collector developed in this study was 400 times higher than that of the MERV 10 filter. Therefore, it was concluded that the two-stage ESP could be a promising PM removal device suitable for subway air conditioning system.