The invention discloses a smart card and an application upgrading method thereof, which relate to the technical field of the smart card. The smart card in the present application comprises a secure storage unit and a processing unit, wherein the secure storage unit is used for storing fixed data of a user; the processing unit is used for deleting other data except the user fixed data in the upgrading process, recovering the user fixed data after downloading the new data, and completing the application upgrading. As that technical proposal of the application is adopted, the user-sensitive datais stored locally without re-writing, and the bi-directional identity authentication between a remote application issuer and a local smart card is ensured through a PKI mechanism during the upgradingprocess, thereby ensuring the identity legitimacy of the upgrading operation.