With the petroleum storage reduction and global warming,there is an increasing need to revolutionize the energy supply chain,especially in the transportation industry. Researches on the production of fuels derived from biological renewable feedstocks have been greatly intensified over the past decade. Sustained researches have been performed with biofuels,such as bioethanol which is the most commonly used in SI engines due to its renewable nature and high octane number. Apart from SI engines,bioethanol is also used in diesel engines. Our country population resources are numerous,it is impossible to popularize the bioethanol in large scale due to the limitation of the area of cultivated land. With the development of fuel production technology,more and more alternative fuel for diesel have been found,such as 2,5-dimethylfuran (DMF). In the past,DMF did not draw extensive attention due to the limitation of production technology. Recently,some significant breakthroughs have been made in production methods for DMF,which makes it is possible to be widely applied as a major alternative fuel for diesel in compression ignition engine. Although DMF is a promising biofuel,little is known on its combustion and emission characteristics. The experiments were carried out on a modified four-cylinder,4-stroke,water-cooled,DICI engine coupled with a common rail fuel injection system using blends of diesel and DMF. Conventional diesel fuel was used as the base fuel. Mixtures of 10% and 30% by mass fraction of DMF with the base diesel fuel were tested in the research,referred to as D10 and D30,respectively. Traditional pure diesel referred to as D0. The experimental conditions were constant engine speed of 1800 r min-1 and loads from 10% to 90% at an interval of 20%,corresponding to 0.13,0.38,0.63,0.88 and 1.13 MPa BMEP,respectively. Unregulated emissions would severely harm the health of humans and other living beings. Some of the unregulated emissions,even in minor quantities into the air,can induce major health problems in large sections of the affected population. There is much research on the regulated emissions of DMF,but rarely on the unregulated emissions of formaldehyde,acetaldehyde or benzene. Airborne particulate matter (PM) is also associated with several severe health hazards. Thus,we studied the combustion and unregulated emission characteristics as well as PM emission from diesel engine on different DMF and diesel blends compared with baseline diesel. The results show that at 0.13 MPa BMEP,with the increase of DMF mass fraction in the mixtures,the peak cylinder pressure decreases significantly and the peak heat release rate (HRR) significantly increases. However,at 0.88 MPa BMEP,peak cylinder pressure and HRR are increased with the increase of DMF mass fraction. 1,3-butadiene,acetaldehyde and benzene emissions are decreased with the increase of engine load. The NO_x emissions increases with the increase of engine load. In addition,DMF blending with diesel increased acetaldehyde emissions,whilst reduced 1,3-butadiene and benzene emissions. At 0.13 MPa BMEP,D30 has the lowest NO_x emissions. For each tested fuels,the nucleation mode greatly dominates the particle size distribution. At 0.38 MPa BMEP,compared with diesel,the particle number concentration of blend fuels are lower in each test mode. However,at high load of 1.13 MPa BMEP,the particle number concentration of diesel is consistently the lowest within the entire range of diameters. At 0.88 MPa BMEP,D30 has 60.5% smaller nucleation-mode number and 232.2% smaller accumulation-mode mass than diesel. D30 has much smaller mean accumulation-mode diameter than diesel (50.9 vs. 60.1 nm).