Crude oil demulsifying agent and preparation method thereof

The invention discloses a crude oil demulsifying agent and a preparation method thereof. The demulsifying agent is prepared by performing cross-linking polymerization reaction on polyether which is shown in a formula II in the specification and used as a raw material and methylbenzene-2,4-diisocyanate which is used as a cross-linking agent, wherein the polyether shown in the formula II is prepared according to a step of sequentially performing oxyalkylation ring-opening polymerization reaction on a compound shown in a formula I in the specification and epoxypropane as well as ethylene oxide under a base catalysis action. On crude oil in the Bohai sea, the crude oil demulsifying agent is high in demulsifying performance under in situ temperature, and the dehydration rate is more than 80 percent when the using amount is 100mg/L and the dehydration time is 60min.