The method for extracting oil in algae according to the present invention comprises: (a) mixing algae and amines so as to dissolve the oil in the algae, thus forming the first solution; b, mixing the hydrophobic ionic liquid with the first solution, stratifying same, and forming an oil and amine plus hydrophobic ionic liquid layer; c, separating the oil from the amine plus hydrophobic ionic liquid layer, introducing carbon dioxide or sulfur dioxide into the amine hydrophobic ionic liquid layer, allowing the amine to form ammonium carbamate, ammonium bicarbonate, ammonium sulfonate, or ammonium bicarbonate salt, and stratifying hydrophobic ionic liquid layer; d, separating the hydrophobic ionic liquid from the ammonium carbamate, ammonium bicarbonate, ammonium sulfonate, or ammonium bicarbonate salt, injecting air or inert gas nto the ammonium carbamate, ammonium bicarbonate, ammonium sulfonate, or ammonium bicarbonate salt so as to return to amine, wherein the amine refers to primary amine, secondary amine or thirdly amine. The method for extracting oil in algae can improve microalgae oil extraction efficiency, and reduce energy consumption for retrieving oil extraction solvent.