The invention belongs to the technical field of oil field sewage treatment, and in particular, relates to a ternary compound flooding produced water deoiling agent; the deoiling agent is a zwitterionic deoiling agent prepared by the steps of carrying out a reaction of 2,5-pyridine diamine with formaldehyde and formic acid to generate an intermediate and then carrying out a reaction of the intermediate with sodium laurate chloride, wherein the molar ratio of 2,5-pyridine diamine to formaldehyde to formic acid to sodium laurate chloride is 1 to (2.5-6) to (2.5-5.5) to (0.8-2.5), preferably (1-3) to 3 to 3 to 1.5. The deoiling agent has the advantages of simple preparation, strong adaptability, low cost, strong salt tolerance and good deoiling effect, the salt tolerance reaches 2.3*10<4> mg/L, and the deoiling rate of ternary compound flooding produced water reaches more than or equal to 97%. Recovered oil produced by separation does not affect subsequent dehydration of crude oil, so the deoiling agent can be widely applied in the deoiling process of the ternary compound flooding produced water.