The invention discloses a prodrug system prepared by connecting a series of oligopolymers synthesized by a group protection and deprotection method and polyethyleneglycol to be used as a drug carrier, belonging to the technical field of chemical drugs. Laden drugs are water-insoluble anti-tumor drugs such as taxol, or other cancer therapy drugs such as doxorubicine and camptothecin. A research discovers that drug compositions prepared by the method greatly improve the hydrophobic nature of the anti-tumor drugs and can accurately control the gather time of the oligopolymers on focus parts and the hydrolyzation rupture time of ester bonds by accurately controlling the lengths of segmers of the oligopolymers so as to control the drug release time so that drugs are stably released, thereby the method prevents burst release causing toxic side effect on normal cells, reduces the drug dosage to enhance the curative effect and sufficiently plays a sustained and controlled release role; and inaddition, the structure of the oligopolymers is accurate, and the molecular weight of synthesized amphipathic block polymers which are uniformly distributed is accurate, thereby the method can ensuresynthesized drug ingredients to be definite and stable and the pharmacokinetics and the treatment effect (activity and toxicity) of the synthesized drugs to have good reproduction quality and be accurately defined.