The present study focussed on a novel phosphorylated corn straw xylans (XYCS-P) that had excellent thermal stability, crystallinity and functional activity and could be potentially used as functional agents in food products. In this work, the phosphorylated derivative XYCS-P was successfully prepared, and the chemical characterisation, spectral analysis, thermal analysis, morphology analysis, antioxidant capacity and anticancer activity were evaluated. The results indicated that XYCS-P possessed superior thermal stability to the native corn straw xylans (XYCS) when exposed to the high temperature (above 240 °C). In addition, the crystallinity of XYCS-P was better than that of XYCS. Moreover, for XYCS-P, the scavenging activity of the hydroxyl radical, (1,1-diphenyl-2-picrylhydrazyl) DPPH radical, superoxide anion radical and the ferric ion reducing antioxidant power were significantly stronger than that of XYCS (P < 0.01). Besides, XYCS-P exhibited a remarkable inhibition effect for HepG2 cells, and the IC 50 value of XYCS-P was determined to be 335.91 μg mL −1 (P < 0.05).