The invention belongs to the technical field of modifying and grinding method for perpendicularity, and particularly relates to modifying and grinding method which meets the perpendicularity requirements of the air bearing thrust end face and the rotation axis for the perpendicularity of the air bearing thrust end face and the rotation axis. The method comprises the following steps of 1 axis determination, 2 bottom end face modifying and grinding, 3 secondary axis determination and 4 thrust end face modifying and grinding. According to the modifying and grinding method, the requirements of a gas spindle on machining precision can be reduced, the cost is effectively reduced, and the yield id increased; the problem that the perpendicularity of the air bearing thrust end face and the rotation axis can only be guaranteed by relaying on the machining precision is broken through.