Abstract: The 1000-hour reliability bench test of diesel engine fueled with B5 biodiesel was completed. The engine parameters such as fuel consumption, lubricant oil consumption, power, torque, piston leakage volume and exhaust temperature before and after the reliability test were measured. The lubricant chromatographic analysis was made, and the main engine parts were disassembled and analyzed. The results showed fuel consumption and oil consumption increased slightly after the reliability test, and the power, torque and exhaust temperature decreased at different degrees while the piston leakage volume increased. The difference of gas emission such as CO between B5 biodiesel and diesel was not too big. The engine lubricating oil contained unsaturated fatty acid methyl ester and aroused lubricant metamorphism. Some carbon deposition exised in the fuel injector, valve and piston, and shadow scratch existed in piston skirt and piston ring attrition normally.