The gas oil which is the main fuel of diesel engine is limited fossil fuel and the depletion in the future is doubted. As an alternative fuel of gas oil in addition fuel temperature injection valve opening pressure and fuel injection timing changed using the fuel in which producible soybean oil in the kerosene in which low calorific value is high mixed to 20〜80% is used and engine performance test was carried out and emission characteristic and change of thermal efficiency were examined.