Combined the roughcast expansion technology for double curvature high rib integral panel part from a certain type of aircraft, a rapid and precise expansion method for the part is realized. The part base expansion method uses geometric simulation modeling method based on the hypothesis of the siding material deformation in thickness direction is negligible and the siding neutral layer surface area is unchanged, and determines reinforced structure and internal milling information on panel body based on mapping theorem and intersection algorithm. Finally, a machine panel as an example, the geometry simulation modeling approach is introduced step by step.