Engine bench tests has been done on a common-rail diesel engine with bio-diesel fuel to study effects of B100 and B20 on output power, fuel consumption and emissions. Test results show that B100 and B20 could reduce PM, HC, CO emission and smoke, but power decrease, fuel consumption increase and NOx increase obviously, B100 reduce PM and DS with $50%{sim}70%$ and $80%{sim}85%$ compared with diesel fuel, while B20 reduce PM and DS with $25%{sim}35%$ and $30%{sim}40%$. NOx of B100 and B20 increase $5%{sim}20%$ compare to diesel.