Abstract: This invention provides a composite type heavy oil demulsifier and its preparation methods. The demulsifier includes two effective constituents. The constituent I is an amino nonionic dendritic polyether and the constituent II is a dendritic ester acid. The structural formula is presented as Formula I and II, respectively. The demulsifier has good abilities in interfacing between oil and water and reducing viscosity. It has good demulsification performance in breaking crude oil emulsion and is useful in heavy crude oil production and petroleum refining.