Aiming at the random-frequency-hopping synthetic wideband radar system as well as the application background of hypersonic vehicle platform, this paper analyzed the large scale Doppler broadening effect and random/non-linear range-Doppler coupling effect, as well as their influence on target range profile. Meanwhile，a method of real-time recursive and mematic imaging algorithm based on Doppler pre-processing was proposed. By this method, the multi-speed-channel range profiles were obtained by using the echo data of current frame and past frames, and Doppler-beam-sharpening was advanced to be performed at the speed channel of target and its adjacent channels to suppress the above special effects caused by high dynamic motion of platform and random frequency hopping in bandwidth synthesis. The recursion was used so that the range profiles of each frame can be obtained from those of the previous frame through adding a few computations. The memory factor was adopted to further reduce the storage and computation costs. Theoretical analysis and simulation results show that the proposed imaging method can effectively improve the imaging quality, and can more easily meet the high-data-rate real-time imaging requirements in the hypersonic platform-borne application.