Biodiesel as a renewable energy is becoming increasingly attractive due to the growing scarcity of conventional fossil fuels. Meanwhile, the development of after-treatment technologies for the diesel engine brings new insight concerning emissions especially the particulate matter pollutants. In order to study the coupling effects of biodiesel blend and CCRT (Catalyzed Continuously Regeneration Trap) on the particulate matter emissions, the particulate matter emissions from an urban bus operated under steady and transient conditions respectively on real road equipped with and without CCRT (the same bus) fuelled with biodiesel blends BD10 (90% pure diesel and 10% biodiesel by volume) and BD0 (100% pure diesel) was tested and analyzed using electrical low pressure impactor (ELPI). Results showed that the particulate number-size distribution of BD10 had two peaks in nuclei mode and accumulation mode respectively except the condition of high speed, which was similar to BD0. In addition, BD10 led to 17.75% smaller average PN (particulate number) emission rate and 26.33% smaller average PM (particulate mass) emission rate under steady condition in comparison with BD0, while under transient condition, PN and PM average emission rates of BD10 were less than that of BD0 by 19.96% and 17.88% respectively. When the bus was equipped with CCRT, its PN concentration decreased substantially both for BD0 and BD10 and the peak in accumulation mode disappeared. Meanwhile, PN and PM average emission rates decreased more than 94% for BD10 and BD0 under both steady and transient conditions and the purification efficiency was more remarkable for BD10.