Abstract: A single epoch algorithm for extracting large deformation from BDS triple frequency carrier phase signal is proposed. Based on the pre-deformation coordinates of monitoring points, this algorithm uses BDS three-frequency signal to construct ultra-wide roadway combination, uses data processing strategy without whole-cycle problem to obtain rough deformation values, and refines the original observation walues of wide roadway and L1 to obtain accurate deformation information step by step. The feasibility of the proposed algorithm is verified by testing a set of measured deformation data on the deformation monitoring test platform.