The invention discloses a platform support temperature deformation resistant automatic positioning mechanism. The mechanism comprises an upper plate, a semispherical part, a ball socket part, a middle-upper plate, pin rollers, a middle plate and a middle-lower plate, wherein the upper plate is connected with the semispherical part; the semispherical part is matched with the spherical surface of the ball socket part; the ball socket part is connected with the middle-upper plate; the middle-upper plate, the middle plate and the middle-lower plate are sequentially laminated up and down; a layer of pin rollers are respectively clamped between the middle-upper plate and the middle plate and between the middle plate and the middle-lower plate, and the two layers of pin rollers have vertical rolling directions; stoppers are arranged on two sides of the middle-upper plate and two sides of the middle-lower plate along the rolling direction of the pin rollers; and four screws are supported against the supporting block at the bottom of the middle-upper plate. The automatic positioning mechanism is a floating device arranged between a lifting platform and supporting stand columns, the relativeposition between the upper platform and the lower supporting stand columns can be adjusted by adopting spherical contact, two-layer pin roller structure and moving limitation, the problem of thermalstress deformation of the supporting stand columns and platform can be solved under a low-temperature and high-temperature state.