The investigation results about physicochemical properties of block copolymers based on ethylene and propylene oxides and their solutions which may be used as demulsifiers for oil emulsions have been represented. The dependence of their physico-chemical properties on the content of oxyethylene and oxypropylene groups in the molecule has been determined. On the basis of the technological suitability a series of block copolymers was chosen and their demulsified ability was examined. The increase of ethylene oxide content in the macromolecule positively affects the blockcoplymer demulsified ability.