Method for controlling symmetry degree of steel rail in straightening process

The invention discloses a method for controlling the symmetry degree of a steel rail in a straightening process. The method comprises the following steps that after rollers of a straightening machine are changed, the steel straightening positions of east and west vertical rollers are calibrated by taking the central axis of the straightening machine as a standard, and the offset +/-Z of the east and west vertical rollers in the straightening process of the steel rail is determined according to the change of the symmetry degree of supplied materials before straightening of the steel rail; before the steel rail enters a straightening machine to be gripped, the positions of the east and west vertical rollers are shifted to the gripped position from the steel straightening position, after the steel rail is gripped, when the torque value of two flat straightening roller motors is larger than 40 KN . M, the positions of the east and west vertical rollers return to the steel straightening position from the gripped p