Kaband millimeterwave SAR with high resolution and clear outline imaging characteristics has drawn great attention among researchers. With the development of Kaband devices, makes KaSAR system a hot research topic in many countries. Digital beamforming (DBF) scanonreceve (SCORE) can avoid overlarge peak transmit power, meanwhile provides adequate system gain, which efficiently solves the power consumption issue in millimeterwave systems. Besides, sliding spotlight mode ensures the high azimuth resolution without restricting the size of the azimuth antenna. According to this, the paper presents a sliding spotlight SAR system based on DBFSCORE, and then provides the imaging flow diagrams, as well as the analytical expressions. Finally, the effectiveness of the algorithm is verified by simulation experiments.