Three-point bending specimen with fixed constraints is a novel small specimen test technique, which can simultaneously obtain creep deformation and creep fracture data. However, the current research only focused on the small deformation theoretical analysis, which is contrary to the actual experiment results. In this study, the general deformation theory was introduced to analyze creep deformation behavior of three-point bending specimen with fixed constraints at the large deformation stage. Based on this theory, the equivalent stress and strain were analyzed. Then, the feasibility and accuracy were verified by comparing with the experimental data of A7N01 aluminum alloy at 380 °C. The results show that the regressed creep parameters agree well with those from the uni-axial ones. It can be found that the equivalent stress obtained by the general deformation theory can be well used to life prediction analysis of A7N01 aluminum alloy.