Abstract: This paper introduced the models of instantaneous uniform stretching, flexural cantilever stretching, and multiphase stretching, with special emphasis placed on their basic assumptions and application conditions. 2D inverse and forward modeling and 1D strain rate modeling have strong superiority on studying the lithospheric stretching factor and rifting process. In the numerical modeling, we often need to combine some models together in order to break through the limitation of the assumptions that existed in each single model, for example, using the flexural cantilever model and multiphase stretching model together to simulate the multi-rifting process. With the purpose of researching the post-rift subsidence characteristics of the Baiyun sag, we use the 2D inverse and forward modeling and 1D strain rate modeling to calculate the lithospheric stretching factor and theoretical thermal subsidence, comparing with the observed post-rift subsidence. The distribution of the lithospheric stretching factor is shaped like a bell, with the maximum value 3.5 in the center of the sag. The observed post-rift subsidence is much bigger than the theoretical post-rift subsidence in the center and south of the sag, with the anomalous post-rift subsidence over 2km.