The invention relates to an air bearing, in particular to a pressure-sharing cavity air thrust bearing which comprises at least one air floatation sliding block; a supporting surface of each air floatation sliding block is provided with at least one pyramid pressure-sharing cavity; the supporting surface is opposite to a substrate; the conical bottom surface of the pyramid pressure-sharing cavityis flush with the supporting surface; the peak of the pyramid pressure-sharing cavity is provided with an orifice; the orifice is communicated with an air supply pipeline which is arranged in the airfloatation sliding block; and the air supply pipeline is communicated with an external pressurizing air source. According to the invention, a diverging pyramid pressure-sharing cavity is adopted so that the high-pressure air more easily flows out along a parallel streamline when the high-pressure air flows in a bearing clearance through the orifice, the bearing vibration phenomenon educed by vortex close to the orifice is restrained, and the harm of micro vibration on the static and dynamic performance of the whole moving system is reduced.