The combustion cyclic variations of DMC/diesel burned in a common-rail engine under different conditions are studied, and the influences of COHR and EGR on combustion cyclic variations are also carried out. Results show that the combustion cyclic variations of different fuels burned in the common-rail engine are relatively small. The combustion cyclic variations of D10 are greater than that of diesel. The combustion cyclic variations at high load are relatively low. With the increase of COHR, the cyclic variations coefficient of pmi are not obvious, while the characteristic parameter for pmax grows slightly and that for θd grows obviously. The rise of EGR rate could cause the slow increase of cyclic variation coefficients of D10 fuel, while that for diesel is relatively smooth. The high mean indicated effective pressure corresponds to short flame developing period.