An experimental study on the removal of harmful particulatematter and hydrocarbons emitted by a gasolineengine using non-thermal plasma was conducted. Nonthermal plasma was found to remove the PM and HC effectively.However, there is a threshold of the energy densityapplied to the NTP reactor such that increasing the energydensity below the threshold promotes the removal rate of PMand HC, whereas increasing the energy density above thethreshold hinders the removal rate of PM and HC. Increasingreaction temperature, prolonging the residence time ofexhaust gas in the reactor and using appropriate catalysts arebeneficial to the removing of the PM and HC.