Abstract The particulate matters (PMs) emitted from marine diesel engine exhaust during the combustion process have low resistivity and extremely small in the range of 70-120nm. These particles cause a various human health and environment impacts. After MARPOL 73/78 Annex VI by International Maritime Organization, shipping-induced NOx and SOx, PM emissions are regulated stricter. This research has been developed an after treatment system for removal of diesel PM from the ship exhaust. The PM was combusted by using plasma assisted catalysis. Non-thermal plasma (NTP) reactor had a coaxial double tube structure. The pellets as a catalyst are packed between the inner and outer tubes. A high-frequency voltage was applied to the reactor, NTP was generated. In the NTP reactor, the air is activated by discharge and produces ozone, oxygen radical and nitrogen radical, resulting the diesel particulates are oxidized under low temperature condition. Diesel PMs are perfectly combusted by ozone produced in NTP. When the gas temperature is higher than 250 degrees, NO in the flue gas is oxidized to form NO2 by ozone and O radical, then carbon particles can be combusted by a reaction with NO2. Moreover, PMs are also combusted by oxidation catalyst. The catalyst used was NS-1A (Nikki-Universal., LTD.). It is spherical and the diameter is about 4mm. In this experiment, the catalysts surfaces depositing the PM were filled into the reactor. PM is taken from the diesel generator was operated with light oil. In the combustion experiment, plasma was generated in the heater which carried out temperature adjustment. It is thought that PMs combust and generate CO and CO2. Therefore, CO and CO2 concentrations before and after the PM combustion were measured and combustion efficiency was determined. From the experimental result, PM combustion efficiency improved by using plasma assisted catalyst. This result shows that the synergistic effect by the plasma and the catalyst can be expected.