The invention discloses an inverse-parabola-shaped retroflexed hem structure of a sealing frame of a gas mask. A retroflexed hem of the sealing frame is composed of a forehead part (1), a temple part(2), a cheek part (3) and a lower jaw part (4), wherein the forehead part (1), the temple part (2), the cheek part (3) and the lower jaw part (4) are all in left and right symmetry; the forehead partis in an inward concave inverse parabola shape, and the cross section shape of the forehead part is expressed as y=0.05x<2> minus 3.3x plus 45; the temple part is in an inward concave inverse parabolashape, and the cross section shape of the temple part is expressed as y=0.014x <2> minus 2x plus 39; the cheek part is in an inward concave inverse parabola shape, and the cross section shape of thecheek part is expressed as y=0.015x<2> minus 2x plus 35; and the lower jaw part comprises a lower jaw side part and a chin part, the lower jaw side part is in a straight shape, the cross section shapeof the lower jaw side part is expressed as y=0.16x plus 0.1, the chin part is in an inward concave inverse parabola shape, and the cross section shape of the chin part is expressed as y=0.024e<0.13x>. The concave surface of the retroflexed hem structure is directly attached to the face, and the physiological comfort of the wearer is improved due to the design of the retroflexed hem structure.