The invention provides a method for determining thicknesses of gaskets for assembling roll to bearing pedestal. The method comprises the following steps that (1) the thickness of the radial gasket isdetermined, concretely, a bearing is assembled in the bearing pedestal, a bearing gland is mounted, and a bolt is fastened by a ''finger tightening'' method, the distance between each of different points on the bearing gland and the end face of the bearing pedestal is measured, and a mean value is taken and is the thickness of the radial gasket; and (2) the thickness of the axial gasket is determined, concretely, by measuring the width of a bearing inner ring and the length of a to-be-assembled roll neck, the thickness of the desired axial gasket is determined, and the nominal axial gasket thickness Ta is equal to W-L+G, wherein W is the width of the bearing inner ring, L is the length of the to-be-assembled roll neck, and G is the specified axial clearance during design. The gasket thicknesses can be determined directly through measurement and simple operation without hoisting the bearing pedestal or the roll.