The structure and aerodynamic performance of the micro-turbine for the micro-machine tool spindle were designed and calculated, and the high speed airflow in the micro-turbine was numerically simulated by the software FLUENT. The analysis has indicated that the micro-turbine torque produced by airflow pressure changes little while that by air viscosity decreases dramatically with the increase of rotational speed at constant supply pressure, which causes a dramatic decrease in the total torque. The back pressure in the micro-turbine chamber increases with the increase of the supply pressure, which seriously affects the rotational speed. The airflow from the micro-turbine nozzle cannot directly go to the corresponding blade, but goes round the blade wheel under the action of the coming flow, which causes great flow loss. Finally the micro-turbine structure was improved and its torque increased by 13%,which satisfied the design requirement.