Hydrostatic forming has recently been applied as a special method for manufacturing products with complex surfaces from sheet or tube metal. However, effects of technological parameters as well as geometrical parameters of die on formability and quality have not been thoroughly studied. It can be seen from research on hydrostatic forming for cylindrical products that the formation of curve radius at the bottom of cylindrical die has a heavy dependence on input parameters: blank holder pressure, liquid pressure, relative depth of die and relative thickness of work piece. Furthermore, small value of curve radius at die bottom is supposed to prevent the formability due to the difference in forming mechanism between hydrostatic forming and conventional drawing. Therefore, it is necessary that the extent to which the curve radius at die bottom relies on the parameters above be evaluated. Using orthogonal second order design, relationships between the parameters and curve radius are studied and presented as functions and graphs. From that, values of curve radius can be suitably defined in different forming modes.