A 3-D combustion model considered the characteristics of Jatropha curcas oil was established, the combustion process of diesel engine fueled with Jatropha curcas oil was simulated. Simulation results of the cylinder pressure fitted well with the results of test. The flow field, temperature field, and mean temperature in cylinder were analyzed by the simulation. It is found that the injection timing is advanced when the engine fueled with Jatropha curcas oil. The timing of combustion is advanced, the peak premixed combustion is also advanced, and the combustion duration is longer than the engine fueled with diesel fuel.