Because of its cleanness and renewability, biodiesel has a great potential as the alternative of diesel fuel to confront with the increasing energy crisis and environment pollution. In this study, diesel oxidation catalyst (DOC) was used to reduce the typical regulated emission and particulate emission. The combined method of fuel design concept with diesel oxidation catalyst was applied in this study.DOC with Pt catalyst was equipped in the engine test bench in this study. The effects of DOC on diesel engine particulate emission fueled with Euro V diesel fuel, biodiesel and ethanol-biodiesel blends were investigated in this study. It was found that DOC seemed have no effects on NOx emission, while it could improve the oxidation reaction from NO to NO2.In the section of particulate emission, DOC could reduce the particulate mass and number concentration, especially in the range of smaller diameter particles. The SOF could be reduced effectively with DOC. With the increase of ethanol, the smaller particles (d<50nm) of ethanol-biodiesel blend fuels were more likely to be oxidized with diesel oxidation catalyst.The relationship between fuel oxygen content and the emission reduction with DOC was investigated in this study. With the increase of fuel oxygen content, the reduction of particulate mass and number concentration with DOC increased. The nano-structure of biofuel particulate and higher NO2 emission of biofuel could prove that the biofuel particulate have great potential to be oxidized. This property combined with DOC could help to improve the regeneration of diesel particle filter (DPF).