An experimental study of particulate matter (PM) emission was conducted on four cars from Chinese market. Three cars were powered by gasoline direct injection (GDI) engines and one car was powered by a port fuel injection (PFI) engine. Particulate mass, number and size distribution were measured based on a chassis dynamometer over new European driving cycle (NEDC). The particulate emission behaviors during cold start and hot start NEDCs were compared to understand how the running conditions influence particulate emission. Three kinds of gasoline with RON 91.9, 94.0 and 97.4 were tested to find the impact of RON on particulate emission. Because of time and facilities constraints, only one cold/hot start NEDC was conducted for every vehicle fueled with every fuel.The test results showed that more particles were emitted during cold start condition (first 200s in NEDC). Compared with cold start NEDC, the particulate mass and number of hot start NEDC decreased by a wide margin. The particulate mass and number reductions of hot start NEDC mainly resulted from ECE cycle sections. The particulate mass and number of cold start ECE were much higher than that of the hot start ECE due to the inhomogeneous mixture combustion process during cold start condition.Gasoline RON had little impact on particulate emission emitted from the four test cars when their engines ran without knocking. However, when the GDI cars calibrated with a high RON gasoline ran with a low RON gasoline, the fierce knocking would occur under high load condition such as acceleration from 100km/h to 120km/h and increase the number of both nucleation and accumulation particles significantly.