Abstract: Real-world particle number emissions from a China Ⅳ diesel bus fueled with three different fuels were studied. The fuels included neat diesel fuel, B20 fuel (20% biodiesel+80% diesel fuel by volume) and G20 fuel (20% gas to liquid 80% diesel fuel by volume). The results showed that size distributions of particle number concentration of the bus fueled with the three fuels were bimodal. The peak value of the nucleation mode particle size was 10.8 nm in diameter, while the peak value of the accumulation mode particles varied between the fuel types:80.6 nm (neat diesel), 69.8 nm (B20 fuel) and 60.4 nm (G20 fuel). Under different road conditions, the bus fueled with neat diesel had the lowest particle number concentration on a fast road, 7.35×10¹⁵particles per kilometer, which was lower by 47.7% and 55.1%, respectively, than the results on a main road and secondary road. For different fuels, the bus fueled with G20 fuel had the lowest particle number concentration with 6.92×10¹⁵ particles per kilometer on the entire road, which was lower by 42.5% and 32.4% compared with the neat diesel and B20 fuel, respectively. Among the particles, for the nucleation mode particles, the number concentration was 1.81×10¹⁵ particles per kilometer, lower by 3.1% and 15.4% than neat diesel and B20 fuel, while for the accumulation mode particle number, the concentration was lower by 49.7% and 37.0%, respectively. This indicates that the gas-to-liquid fuel can effectively reduce the particle emissions from diesel buses.