Characteristics of regulated and unregulated emissions of biodiesel blends（derived from waste oil）in a common rail diesel engine without any modification were investigated. The results showed that NOx emissions increase significantly with a higher blend ratio and NO2 concentration increases after two diesel oxidation catalysts. A linear relationship between the reduction of smoke number and the blend concentration is found. For unregulated gas emissions, MECHO emission is reduced with a higher blend concentration of biodiesel at full load as combustion improvement. Due to low sulfur of biodiesel, the range of SO2 reduction is between 20%～60% for pure biodiesel compared with diesel. Particles in nucleation mode are dominated by the sulfur content of biodiesel blends. Concerning the pure biodiesel, total particle number concentration is reduced due to the lowest sulfur content.