In order to improve high temperature resistance and dehydration performance of demulsifier for oilsand emulsion treatment，phenol-amine resin containing dinaphthol structure was synthesized using 6，6-isopropylidenebisnaphthol，ethanediamine and methanol as the raw materials. Then multibranched high temperature resistant demulsifier was further synthesized using the phenol-amine resin as the initiator，KOH as the catalyst，through addition reaction with epoxyethane and epoxypropane respectively. High temperature resistance was studied by thermogravimetric analysis and hydroxyl value，dehydration performance was evaluated by high-temperature dehydration bottle tests. The results showed that the demulsifier had good temperature resistance with little mass loss below 350℃ and the stable hydroxyl value when temperature was at the range of 100—300℃，indicating that the demulsifier could be used to treat oilsand emulsion in the high temperature environment. For the oilsand emulsion from oilfield in Alberta，Canada，the dehydration rate reached up to 90% within 8 hours at the demulsifier dosage of 400 mg/L and at the temperature of 130℃ ，which was higher than that of the incumbent demulsifier. The obtained demusifier have excellent demulsification and dehydration performance for the oilsand emulsion.