Abstract: The bistatic SAR overall slant range history of target response is essentially different from the monostatic slant range history; hence, bistatic SAR imaging processing can not be achieved by purely monostatic approaches. To address the problem, a wavenumber domain algorithm is derived, which is based on the one-order approximation of the point scatter responses two-dimensional spectrum phase. Bistatic SAR data of simulated point and surface scatter response are focused by the algorithm and the quality of the image demonstrates the effectiveness and high resolution of the algorithm in large squint angle and large base line length case.