The invention relates to polymer nano-particles for loading alkaline antitumor drugs. A polymer material forming the nanoparticles has biological compatibility and biodegradability, and the polymer material loads the alkaline antitumor drugs; and the polymer material comprises liposome, polylactic acid, polylactic acid-glycolic acid copolymer, polycaprolactone, chitosan, albumin and cyclodextrin; and the alkaline antitumor drug is a micromolecule antitumor drug with pKa being more than 7.4 and comprises adriamycin, pharmorubicin, taxol, docetaxel, vinblastine, vincristine, topotecan and alkaloid Chinese medicine monomers. The polymer nano-particles solve the defects that the pH dependence and physiological drug fastness cannot be reversed. The polymer nano-particles are free from introducing additional drugs, so that the influence on the internal environment of an organism is small, the pH dependence physiological drug fastness is reversed through the polymer nano-particles, not only is the effect realized, but also since no influence is caused for the internal environment of the organism, the polymer nano-particles are safe to use, little in side effect, and wide in application range.