Abstract: The imaging efficiency of the synthetic aperture radar installed in near space slow platform is low. In this paper an imaging mode based on the azimuth multi-beam switching is proposed. The basic idea is to divide the azimuth swath into multiple azimuth sub-swaths. The required pulse repeated frequency is increased accordingly. In the azimuth sampling positions, the azimuth sub-swaths are illuminated periodically. In contrast to the traditional stripmap mode, the proposed mode can improve the imaging efficiency effectively. When the number of the multi-beam is large enough, the imaging efficiency of the slow platform can be higher than that of the fast platform. The high resolution wide swath imaging, meanwhile, can be achieved. The formulas for calculating the key parameters of the system as well as the signal processing steps are provided. The simulation results verify the validity of the proposed imaging mode and signal processing steps.