Abstract: Based on the different properties between Daqing and Gudao crude oils, the applicability of some demulsifers were estimated. Furthermore, new demulsifers were synthesized, and the effect of demulsifer composition on desalting ability of crude oils was approached. It is showed that there is a distinct difference between HLB valves of demulsifers suitable for Daqing and Gudao crude oils, and the desalting efficiency for both oils will be enhanced if the molecular weight of demulsifers are increased.