In order to improve the fuel properties and diesel combustion of biodiesel, waste vegetable oil methyl ester (from rapeseed and soybean oil mixture) with 5-20 mass% 1-butanol (BWME) are tested using a DI diesel engine. The viscosity and pour point of BWME decrease by blending 1-butanol. There is no problem in the startability and stability of the engine operation with BWME. Thermal efficiency of BWME is almost the same as that of the gas oil. The smoke emission decreases with increasing 1-butanol although the HC and CO emissions increase due to the longer ignition delay. It is concluded that BWME can be utilized as an alternative diesel fuel. Furthermore, to improve the ignitability and exhaust emissions of biodiesel with 1-butanol, palm oil methyl ester (PME) with high cetane number is tested as a base fuel of the 1-butanl blend. When the 1-butanol content in PME/1-butanol (BPME) is 15 mass%, BPME has almost the same ignition delay and HC and CO emissions compared with the gas oil. From the experimental results, it is concluded that PME is better than rapeseed oil methyl ester as a base fuel of the biodiesel with 1-butanol due to the better ignitability and lower exhaust emissions.