As a wide-field super-resolution (SR) technique, structured illumination microscopy (SIM) features the merits of fast imaging speed, low excitation intensity and a large field of view. However, it is hard for SIM to realize real-time imaging as the SR-image restoration always time-consuming. The basic workflow for conventional SIM reconstruction is based on the frequency domain reconstruction (FDR), which inevitably brings some computational errors and slows down the image reconstruction speed. In this letter, we introduce a fast SIM reconstruction scheme named spatial domain reconstruction (SDR) algorithm, which allow for obtaining a much faster reconstruction than FDR, making it suitable for real-time SR imaging. Meanwhile, the validity of the SDR algorithm is verified by real experiment. © 2018 SPIE.