Tests were performed with a light-vehicle diesel engine. Four representative operating conditions in 1600r/min speed have been considered. This article compares the combustion and emission characteristics of engine fueled with Bio-diesel and standard diesel. The results showed that the ignition delay time and combustion duration shorten when fuel with bio-diesel. Bio-diesel contains more oxygen and that contribute to complete combustion of fuel. The combustion of bio-diesel fuel results higher NOx emission and lower HC、CO emissions at all operating conditions. But lower Soot emission because of bio-diesel dose not contains sulfides. At the same time, fuel consumption higher, because calorific value of bio-diesel is lower than standard diesel.