Based on present study status of the start and stop life of hemispheric aerodynamic bearing gyro motor which was used for the heart of the high precision and long-life three-bearing gyroscope, designing theoretical and key technical means of hemispheric aerodynamic bearing were studied in this paper. Spiral groove parameters and bearing gap which affected the gas bearing performance and start and stop reliability were two key factors. Groove parameters were used as variables, and variation trends of gas bearing mechanical properties were analyzed by variables. Curves of relation between designing parameters of spiral groove and stiffness of gas bearing were drawn up. Distortions of gas bearing parts in the work at a high speed and at the operating temperature were simulated, and the gap of aerodynamic bearing was sure to be designed reasonably. A hemispheric aerodynamic bearing permanent magnetic gyro motor was invented in this paper and finished start and stop times no less than 3 000 in the start-stop experiment. It indicates that these designing technical means were feasible and suitable for utilization in the high precision and long-life gyroscope.