For the sake of achieving the feeding system to be automated designed, the automatic merging model of the casting hot spot set up based on Casting CAE, and based on this model the riser and cold-iron designs can automatically be completed. The CAD/CAE software system was developed for the steel casting, and the feeding system of the side frame casting was designed by the software. according to the process parameters that were provided in the paper, the sample casting was poured and dissected to determine the volume of shrinkage cavity of sample castings. The results showed that no shrink defect exists in the casting, so it proved that the model was reliable for the riser and cold iron design.