The invention relates to a carbonate polymer containing a functional group of disulfide five-membered ring in the side chain and application thereof. Said polymer can be prepared from the cyclic carbonate monomer containing a disulfide five-membered ring functional group through the activity controllable ring-opening polymerization. For the polymer, the molecular weight is controlled, the molecular weight distribution is narrowed and does not require the protection and deprotection procedures. The polymer prepared from the said carbonate monomer through the ring-opening polymerization has biodegradability, can be used for controlling drugs release system, and can be used to prepare tumor-targeted nano-drug carrier which is sensitive to reduction and is reversible cross-linking, can support long circulation in the body, in high concentration of cancers cells can rapidly release cross-linking in the cancer cells, to release drugs, to kill cancer cells with high efficiency and specificity. The biodegradable polymer has a good application value in the tissue engineering and bio-chip coating.
