To meet the fast imaging requirements of long-orbit ultra-high resolution W-band synthetic aperture radar（SAR）， this paper proposes a graphics processing unit（GPU）-based ω-K real-time imaging algorithm which adopts parallel architecture and double stream multithreading processing. The default stream processes data along the direction of the physical principle. Firstly， it parallelizes the rang compensation， error correction， zero filling and other operations， and then adopts one-layer nested interpolation method. By maintaining the upper and lower dependencies and synchronization management， it can achieve a speed ratio of about 30. The blocking stream starts at the same time as the default stream， generates the parameters and functions required by the default stream， and stores them into video memory before execution， which can greatly reduce the running time of the algorithm. Meanwhile， by setting events on the default stream， the two streams can be executed synchronously in parallel. Experimental results show that the total acceleration ratio of the algorithm can reach about 13， and the relative errors of amplitude and phase are close to 0， which not only has good real-time performance and focusing performance， but also maintains good imaging effect.