Abstract: In order to analyze the combustion noise and the fluctuation of multi-cycle combustion noise at idle condition of the diesel engine using curcas oil, the multi-cycle cylinder pressure at idle condition fueled with diesel, diesel-curcas mix oil, curcas oil and heated curcas oil were collected from a water-cooled four-stroke single cylinder diesel engine. The combustion noise and fluctuation of combustion noise were analyzed by maximum combustion pressure, pressure rising rate, pressure rising acceleration, cylinder pressure spectrum and A sound pressure level. The cylinder pressure spectrum burning diesel was similar to burning diesel-curcas mix oil, and burning curcas oil was similar to burning heated curcas oil. The cylinder pressure was high burning diesel and burning diesel-curcas mix oil. The combustion noise increased with increasing maximum pressure rising rate and with delaying corresponding phase of maximum pressure rising rate at the same condition. The A sound pressure level burning heated curcas oil was about 7 dB lower than burning diesel with 18°CA fuel supply advance angle, and was about 5 dB lower than burning diesel with 21°CA fuel supply advance angle. The fluctuation of the A sound pressure level decreased with the decreasing in cycle variation rate of the maximum combustion pressure rising rate.