Abstract: Finite element software Marc was used to simulat the superplastic forming (SPF) process,predict the thickness of the forming parts and forming results and get the optimized curves of pressure-time loading curves.The SPF and back-pressure forming tests for the AA5083 aluminum alloy were performed at the back-pressure of 0 and 3.5 MPa.The results show that the larger the strain,the less uniform the thickness.The thinnest position of the plates was located at the cone roof of the forming part and the predicted thickness was good agreement with the experimental result.The larger the strain,the larger the volume fraction of cavities.The increase of the back-pressure could effectively inhibit the cavity formation and improve the forming limit significantly.