The need for gasoline particulate filter (GPF) technology is expected to grow with the increasingly tight PM standards being implemented in US, EU, China and elsewhere. Derived from the successful experience with Diesel Particulate Filter (DPF), GPFs inherited the featured alternatively plugged honeycomb structure to provide large filtration area and porous cordierite wall for gas flow and particle filtration. However, unlike diesel particulate filter (DPF), the continuous soot regeneration in GPF makes it difficult to grow and sustain a soot cake on the filter wall, which serves as a highly efficient filter layer in the case of DPF. Therefore, filtration performance of GPFs at zero or low mileage relies heavily on the porous structure of filter media, which is determined by both the substrate and the washcoat being applied. In this work, filter performance including particle number filtration efficiency, particle mass filtration efficiency and backpressure will be characterized using both aerosol test bench and engine dynamometer. Coated or non-coated GPFs with or without low mileage accumulation will be investigated. Based on the results, the impact of washcoat and low mileage accumulation on the filter performance will be discussed.