NOVELTY - Preparing tumor microenvironment-sensitive polysaccharide nanoparticles, comprises e.g. mixing polysaccharide solution with an aqueous initiator solution, adjusting pH, and stirring to obtain polysaccharide having enough free radicals, adding high water-soluble or low water-soluble olefin monomer, and polymerizing to obtain a polymer which is self-assembled with the polysaccharide to form nano aggregate system, adding an environmentally sensitive disulfide or diselenide crosslinking agent, and reacting to obtain polysaccharide-based nanoparticles, then removing impurities, and freeze-drying.    USE - The method is useful for preparing tumor microenvironment-sensitive polysaccharide nanoparticles (claimed).    ADVANTAGE - The method: is efficient and convenient; has high product yield and low cost; and produces nanoparticles having high solids content and uniform particle size; and is environmentally friendly.    DETAILED DESCRIPTION - Preparing tumor microenvironment-sensitive polysaccharide nanoparticles, comprises (i) dissolving water-soluble polysaccharide in water to obtain polysaccharide solution, (ii) dissolving an initiator in an aqueous solvent to obtain aqueous initiator solution, (iii) mixing polysaccharide solution with aqueous initiator solution under inert gas atmosphere, adjusting pH using an acid, and stirring to obtain polysaccharide having enough free radicals, (iv) adding high water-soluble or low water-soluble olefin monomer of formula (I), stirring, polymerizing to obtain a polymer which is self-assembled with the polysaccharide to form nano aggregate system, (v) adding an environmentally sensitive disulfide crosslinking agent of formula (II) or diselenide crosslinking agent of formula (III) before the formation of nano aggregate system to improve stability of the system, and reacting to obtain a solution containing polysaccharide-based nanoparticles, then (vi) removing impurities from the resulting solution, and (vii) freeze-drying the purified nanoparticles to obtain final product.    R1-R9 = not defined.