The invention belongs to the field of organic macromolecular synthesis and drug preparation, in particular to a modification method and product of an antitumor drug with alcoholic hydroxyl group. An RAFT reagent with carboxyl is used for esterified modification to obtain a functional drug, then PEG-A molecules are polymerized onto the functional drug by adopting an RAFT polymerization method, so that the modification of the antitumor drug can be realized; the hydrophilic performance can be greatly improved, and the dissolution and transportation of the drug in the water can be facilitated; andmeanwhile, the functional drug enters the human body after being subjectedto polymerizationed modificationed, under the enzyme catalytic effect, the RAFT reagent and the PEG-A can be degraded and reduced to active drug to play the curative effect, the drug effect can be completely reserved, and the toxicity and side effects of the drug can be avoided.