The invention provides a heat treatment anti-deformation device for a thin-wall annular piece. The heat treatment anti-deformation device can control the deformation amount of the thin-wall annular piece in heat treatment within a specified range. The inner diameter of an annular clamp body is larger than the outer diameter of the thin-wall annular piece, and the axial width of the annular clamp body is also larger than the axial width of the thin-wall annular piece. Three or more radial positioning mechanisms distributed uniformly along the circumference are arranged on the annular clamp body. Each radial positioning mechanism comprises one or more radial through holes, positioning blocks, positioning connecting pieces and positioning adjusting pieces, wherein the annular clamp body is provided with the radial through holes, the positioning blocks, the positioning connecting pieces and the positioning adjusting pieces. Each positioning block is an arc strip-shaped block with the radian of the outer wall is the same as the radian of the inner wall of the annular clamp body, the radian of the inner wall is the same as the radian of the outer wall of the thin-wall annular piece and the axial width corresponding to the axial width of the thin-wall annular piece, is located between the annular clamp body and the thin-wall annular piece and connected with the inner end of the corresponding positioning connecting piece. The positioning connecting pieces are assembled in the radial through holes, and the outer ends of the positioning connecting pieces are connected with the positioning adjusting pieces located outside the periphery of the annular clamp body in a mode that the radial positions are capable of being adjusted.