In this paper, the parallel flight squint mode of airborne Bistatic Synthetic Aperture Radar (SAR) is discussed, and we present an improved bistatic Rang-Doppler (RD) algorithm which used to solve the coupling between the range and the azimuth of this mode. The simulation results prove the availability of this algorithm. We also use this improved bistatic RD algorithm to process the practical flying experimental data, and well focused Bistatic SAR images are generated successfully. Comparing with the standar RD algorithm, the improved bistatic RD algorithm can obtain much better imaging results in the parallel flight squint mode.