Instant catapult steam explosion (ICSE) was applied to treat rice straw for isolating high quality cellulose. After ICSE treatment under the condition of maintaining the pressure at 2.0 MPa for 11 min, the hemicellulose content decreased to 3.70% from the original 20.10%, and the content of α-cellulose was 72.02%. The enormous explosion power density provided by ICSE turned rice straw into cellulosic fibers with good accessibility, as well as it protected the cellulose fibers from being over-hydrolyzed. All of the straw cellulosic samples were analyzed by scanning electron microscopy (SEM), Fourier transformation infrared spectrometry (FTIR), and X-ray diffraction (XRD) to collectively examine the impact of ICSE treatment on the structure and morphology of the cellulose components. The recycled lignin was also analyzed by two-dimensional nuclear magnification resonance spectrometry (2D NMR) to understand the mechanisms underlying the ICSE treatment.