In this research, the extraction conditions of natural dyes from Sarsaparilla root were analyzed by response surface method, and the interaction between extract factors and their significant effects on sarsaparilla root extraction efficiency were discussed. The main components of Sarsaparilla root extraction were investigated by ATR-FTIR and chromogenic reaction, and the stability results of Sarsaparilla root extraction indicated that sarsaparilla root extraction obtained well thermal stability within the range of 60–100 ℃ as well as acceptable pH stability. The ATR-FTIR and XPS were obtained to confirm that the cationic modifier was fixed on the cellulose fiber through covalent bonds in the synchronous inkjet printing process, and the effect of cationic modifier’s alkyl chain length on the inkjet printing performance was clarified by Gaussian simulation calculation. The colorfastness of Sarsaparilla root natural dye ink was further improved by post-mordant treatment, and the mechanism of colorfastness improvement was elucidated by UV-Vis spectrophotometer. The inkjet printed cotton fabrics with CHPTAC-8 ink and Sarsaparilla root ink indicated well UV protection (134.87) and antibacterial property against both Staphylococcus aureus (96.3 %) and Escherichia coli (99.1 %). •The extract conditions was analyzed by response surface method.•The chemical composition of the Sarsaparilla root extract were investigated.•The inkjet printed cotton fabrics obtained well UV protection and antibacterial property.