The fast factorized backprojection for bistatic SAR algorithm (BiFFBP), which processes the bistatic SAR data in more than one beam forming stage, is presented in this paper. The algorithm is developed on the bistatic fast backprojection algorithm SAR (BiFBP) and inherits time-domain characteristics such as unlimited scene size, real time processing, local processing, manageable motion compensation, and large range migration handling. Also, the algorithm works well with different kinds of bistatic configuration. For these reason, it is very suitable for UWB bistatic SAR processing. The proposed algorithm is tested successfully with simulated UWB bistatic SAR data.