The invention relates to a reduced response camptothecin prodrug monomer as shown in a formula I, reduced response camptothecin polymeric prodrug amphipathic molecules of the reduced response camptothecin prodrug monomer, and a preparation method and application of the reduced response camptothecin prodrug monomer and the reduced response camptothecin polymeric prodrug amphipathic molecules. In the formula I, each i is 2 or 3 independently, each X is O or NH independently, and R is H, CH3 or CH2CH3. According to the preparation method, raw materials including camptothecin, triphosgene and the like are used for modifying 20 bits of hydroxyls of camptothecin to prepare a camptothecin prodrug monomer containing disulfide bonds, then the camptothecin prodrug monomer is subjected to high-conversion-rate polymerization by using active free radical polymerization method to obtain an amphiphilic polymer which contains a camptothecin drug repetitive unit and has an extremely high drug loading capacity (more than 50wt%), and in a tumor cell reducing environment, a side chain disulfide bond is broken to perform molecular rearrangement and release camptothecin prodrug molecules, so that the amphiphilic polymer has characteristics of a reduced response controlled-release raw drug. The polymeric prodrug amphipathic molecules improve the water solubility and stability of the drug and have a controlled release characteristic.