A numerical analysis of superplastic blowforming under axi-symmetrical deformation with controlling maximum strain rate was performed. This method of analysis is able to account for the strain hardening with regard to strain rate of formed material. The strain rates of each portion in the formed material are estimated by theoretical equations. The equations are based on stress-strain curves on a superplastic tensile test under certain strain rates as far as the magnitude of strain caused in some actual processes. A forming experiment was carried out with the condition calculated by the analysis method on a truncated cone die for 7475 Al-alloy. The deformation process and variation of thickness on the truncated cone formed under analyzed condition was good agreement with the result predicted by the calculation. By using this analysis method, superplastic blow forming of the hemispherical dome which was controlled for the thickness distribution to be in uniform, was planned. The blank sheet was supplied from the bottom of a conical pan designed by the analysis for the preforming. The bottom of the pan was reformed to the hemispherical dome on the final forming. As a result, the dome was formed with uniform thickness distribution successfully, and this verified the validity of the analysis method and the effect of control on thickness of superplastic formed parts.