The air-lubricated pneumatic workbench introduced in this paper is used in rotary ultrasonic machining which are widely used to machine hard and brittle materials. It is necessary to use special ultrasonic machine tool for rotary ultrasonic machining in the traditional ultrasonic machining, limiting the application of ultrasonic machining. A new type of rotary ultrasonic grinding cutter is developed, which can be mounted on the general purpose machine tool used to machine the hard brittle materials. The air-lubricated pneumatic workbench on which the workpiece is fixed can be used to precisely control the force between the workpiece and rotary ultrasonic grinding cutter when machining. Based on the experimental results of the pneumatic workbench which has been manufactured we find that the force between the workpiece and rotary ultrasonic grinding cutter can’t be easily controlled for the rolling bearings used in such workbench and the rolling friction force between the rolling bearing and guide way. This paper describes a novel pneumatic workbench where we replace the rolling bearing with air bearing which introduces essentially zero friction between the air bearing and guide way. The stiffness of the air-lubricated pneumatic workbench has been calculated in this paper.