Both across-track and along-track baselines exist in Distributed Small Satellite Synthetic Aperture Radar (DSS-SAR). The along-track baseline would bring the Doppler frequency difference between SAR images, which complicates the correlation of DSS-SAR signal. According to the model of the single-look complex SAR images in DSS-SAR, a more exact correlation model of single-look complex images for DSS-SAR was proposed. The new model was derived taking into account both of across-track baseline and along-track baseline in DSS-SAR and would describe the signal more accurately. In the end, computer simulation is given and the results validate the correction of analysis in this paper.