The invention discloses a framework-preposed oil seal used under a high pressure. The framework-preposed oil seal comprises a framework and a sealing body; the section of the framework comprises four line segments; the lower end of a first line segment and the left end of a second line segment are connected and form an included angle A which is equal to 90-100 DEG; the second line segment is horizontal; the right end of the second line segment and the lower end of a third line segment are connected and form an included angle B which is equal to A; the upper end of the third line segment is connected with the left end of a fourth line segment which is horizontal; the upper surface of the sealing body is completely fitted and bonded with the lower surface of the framework; the framework is preposed between a sealing region and hydraulic oil; the peripheral surface of the sealing body has no taper; the outer side of the upper end surface of the sealing body is provided with a fillet; a lip body at the inner circumference of the sealing body is triangular; the internal diameter of the lip body is smaller than that of the framework; and the lip body and the lower end surface of the sealing body are provided with inclination angles. By using the oil seal, the pressure endurance capability of the oil seal can be remarkably improved, and the temperature rise rate of the oil seal in a high-pressure use process can be reduced.