Abstract: Abstract: In order to study the influence of different categories of oxygenated biofuels on the performance and emissions of a diesel engine in a high-altitude anoxic condition, comparative experiments on a horizontal two cylinder diesel engine by use of three fuels: pure diesel, ethanol-diesel E10 (containing 10% ethanol in volume percentage and 90% petroleum diesel in the blend fuel), and biodiesel-ethanol-diesel B10E10 (containing 10% biodiesel, 10% ethanol, and 80% petroleum diesel) blends were carried out. In the process of the test, the engine was not adjusted or modified. The test results showed that when fueled with the E10 and B10E10 oxygenated blended biofuels respectively, the power performance of the diesel engine decreased, and the average drop of the engine brake torque at full-load are 4.24% and 5.49%. And the brake specific energy consumptions (BSEC) of the blended fuels were basically lower than those of the diesel fuel, and the fuel economy improved. The properties of the blended fuels had effects on the changes of the engine fuel economy, and the changes were also related to the engine speed and load. When fueled with the E10 blended fuel, the carbon monoxide (CO) emissions of the engine increased at low loads and decreased at high loads. The hydrocarbon (HC) emissions of the engine were higher than those of the diesel fuel and the percentage range of increment was 4.9%~27.4%. And the nitrogen oxide (NOX) emissions were lower than those of the diesel fuel at low loads, which tended to be the same level of the diesel fuel at high loads. When fueled with the B10E10 blends, the carbon monoxide (CO) emissions and the hydrocarbon (HC) emissions of the engine tended to be the pure diesel fuel level at low loads and decreased at high loads. And the nitrogen oxides (NOX) emissions decreased at low loads, and increased at high loads. The soot emissions of the engine with the E10 and B10E10 fuels both decreased. The hydrocarbon (HC) emissions, the soot emissions, and the carbon monoxide (CO) emissions at low loads of the diesel engine fueled with the B10E10 fuel were all lower than those of the E10 fuel, while the nitrogen oxide (NOX) emissions were basically higher than the E10 fuel level. Compared with the E10 fuel, the B10E10 blended fuel had a better effect on the improvement of the carbon monoxide (CO) emissions, the hydrocarbon (HC) emissions, and the soot emissions of the diesel engine. But the decline in the engine power performance was larger, and the nitrogen oxide (NOX) emissions increased. The study can provide a reference for the application of oxygenated biofuels in high-altitude anoxic regions.