Emulsified fuel from biomass pyrolysis derived bio-oil and diesel was prepared and fueled to a laboratory diesel engine tester. The experimental bio-oil was obtained from the pyrolysis of corn stalk powders in a fluidized bed reactor. The emulsified fuel was produced by mixing the bio-oil with commercial No.0 diesel oil as well as surfactants using a homogenizer. The performances of bio-oil/diesel oil emulsified fuels with two different bio-oil/diesel oil ratios were tested on a ZS1110 diesel engine. Consequently, the load characteristic and exhaust emission characteristic curves of diesel engine were determined, and the specific fuel consumption and effective thermal efficiency of the engine fueled with the emulsified fuel were analyzed in comparison with that of the pure No. 0 diesel oil. The experimental results show that, when the engine is fueled with the emulsified fuel at bio-oil concentration of 15%, the specific fuel consumption is lower and the effective thermal efficiency is higher than that of the pure No.0 diesel oil. The highest fuel saving rate reached 10%. Moreover, the NO and CO emissions are lower than that of the pure No.0 diesel oil.