A micro-high-speed bearing test rig has been designed and fabricated to develop air bearings for a micro-machine gas turbine. The micro-machine gas turbine requires bearings of diameter 4 mm to operate stably at 870 000 rpm. Based on the preliminary analysis, it has been found that a large bearing gap and very high rotor balance are required to achieve low viscous loss at high speed and to prevent the rotor from hitting the bearing at critical speed. Therefore, a hydro-inertia gas bearing has been selected with half-split bearing sleeves. A hydro-inertia bearing is a type of static air bearing which has large bearing clearance to generate supersonic flow in the bearing gap. Currently, a rotor speed as high as 770 000 rpm has been achieved in the test.