Abstract: Through Fischer-Tropsch (F-T) synthetic process, coal can be converted to F-T diesel fuel that has high cetane number, very low sulfur and aromatic contents. This paper presents the research results of an unmodified single-cylinder direct injection diesel engine operating on F-T diesel fuel. The indicated pressure diagrams and injector needle lifts were recorded and the combustion and emission characteristics were evaluated and compared with those of conventional diesel fuel operation. The results showed that F-T diesel fuel exhibits a 18.7% average shorter ignition delay, a 26.8% average lower peak value of premixed burning rate, a higher maximum diffusive burning rate and a comparable total combustion duration when compared to conventional diesel fuel. In addition, F-T diesel engine has a slightly lower peak combustion pressure, a far lower rate of pressure rise, and a lower mechanical load and combustion noise. The brake specific fuel consumption is lower and the effective thermal efficiency is higher for F-T diesel fuel operation. CO, HC, NOx and smoke emissions with F-T diesel fuel are reduced at all test speed-load points when compared to conventional diesel fuel. On average, NOx and smoke emissions are reduced by 16.7% and 40.3% respectively with F-T diesel fuel. The study demonstrates that F-T diesel fuel is an excellent clean alternative fuel for diesel engines.