Abstract: Tahe heavy oil has the characters of high asphaltene content and mechanical mixture. An oil soluble demulsifier by graft copolymerization of polyether and polyacrylic acid was synthesized aiming at the properties of the crude oil. The effect of synthesis conditions, such as synthesis routes, amount of acrylic acid and initiator, and dropping temperature of acrylic acid, on the performance of product was investigated. A complex demulsifier RP-04 was then prepared by combination of the oil soluble demulsifier and an aid agent. The laboratory continuous evaluation test shows that the water content in 3 level desalting and dewatering crude treated by the RP-04 and the reference demulsifier on-the-spot is 0.09% and 0.70%, respectively，and the salt (NaCl）content is 7 mg/L and 9 mg/L, respectively. When the demulsifier RP-04 was used together with desalting aid agent, the total chloride of treated oil is reduced from16 μg/g to4.9 μg/g.

Key words: Tahe heavy crude oil, demulsification, polyacrylate polyether, mechanical impurities