Abstract: Based on national standard method of petroleum products copper corrosion test (GB/T5096-1990), the corrosion character on copper in cottonseed oil methyl ester(CSOME) and cottonseed oil ethyl ester(CSOEE) were detected at 25℃ and 50℃. At the same time, the physical-chemical performances of the two samples were investigated and compared to diesel before and after corrosion. The results showed that variations of the corrosion phenomenon on copper which immersed in the two samples for two months at the 25℃and 50℃. The corrosion property of CSOME was changed seriously. Under the condition of 25℃,the copper corrosion rate was 0.0926?cm/d, and the acid value , the peroxide value, the kinetic viscosity increased by 10.4, 1.44, 1.13 times, respectively. Copper corrosion rate was 0.4115?cm/d and acid value, peroxide value,kinetic viscosity increased by 12.8, 2.16, 1.35 times respectively with temperature rising up to 50℃. The variations of corrosion rate and properties of oils changed seriously with the temperature increasing. The corrosion character of CSOEE had the similar to the CSOME. The changes of diesel was slightly. The copper corrosion was ascribed to degradation of biodiesel. Data of copper corrosion could contribute to industrial application of CSOME or CSOEE.