Abstract: The influence of the bio-lubricating-oil additive was determined by the emission experiment of the diesel engine bench test. The test procedure followed Road vehicles - Engine test code – Performance (GB/T 18297—2001) and Limits and measurement methods for exhaust pollutants from compression ignition and gas fuelled positive ignition engines of vehicles (Ⅲ, Ⅳ, Ⅴ) (GB 17691—2005). The engine speed of 2000 r/min was chosen to conduct the load characteristic test, with CO, THC, NO_x and particulate matter in the exhaust gas collected and analyzed. The results show that the specific THC and CO emissions generally change little, and decreased only at low load, with the maximum reduction of about 15%. The specific NO_x emission increased to a certain extent, with a maximum of rate 15%. The specific particulate concentration could be reduced significantly, with maximum rate of 53%. After using the additive, the particle number concentration of 20~100nm can be reduced at low load, the particle number concentration does not change obviously at medium load, the particle number concentrations below 20 nm and above 50 nm will be reduced at high load, while the particle number concentration of 20~50 nm will be slightly increased. With the increase of the engine load, the particle size distribution map will gradually increase and become narrow and shift to the left, and the use of additives will mitigate the trend.