Optical vortices have the main features of helical wavefronts and spiral phase structures, and carry orbital angular momentum. This special structure of visible light has been produced and studied for various applications. These notable characteristics of photons were also tested in the extreme-ultraviolet and X-ray regimes. In this article, we simulate the use of a simple afterburner configuration by directly adding helical undulators after the SASE undulators with the Shanghai Soft X-ray FEL to generate high intensity X-ray vortices with wavelengths ～1 nm. Compared to other methods, this approach is easier to implement, cost-effective, and more efficient.