The invention relates to a preparation method and application of targeted co-supported drug delivery system nano-particles based on polylactic-co-glycolic acid (PLGA), which can effectively solve the problem of preparing the targeted co-supported drug delivery system nano-particles based on polylactic-co-glycolic acid, and realizes the application in cerebral tumor targeted treatment medicines. The method comprises the following steps: connecting Angiopep-2 by utilizing the reactive amino group on chitosan: reacting chitosan with 3-maleimidopropionic acid N-hydroxysuccinimide to enable the amino terminal of chitosan to have maleimide; reacting with terminal-sulfhydrylated Angiopepe-2 to obtain a chitosan-angiopep-2 polymer. The polymer can be applied to preparation of a PLGA-based targeted co-supported drug delivery system. The method is stable and reliable, the product has a good using effect, small-molecular chemical drugs and genetic drugs can be delivered at the same time, or a fluorescent probe can pass through a blood brain barrier and enters the brain while chemotherapeutic drugs are delivered, and targeted cerebral tumor treatment can be synergized or targeted cerebral tumor treatment and diagnosis can be integrated into a whole.