An unlock method and system for an air-conditioning unit. The unlock system includes: a display apparatus; an input apparatus; and a control apparatus in communication with the display apparatus and the unlock system is configured to perform the following operations: generating a dynamic graphic according to at least an identification code and an update code; generating an unlock password according to at least a certificate, the identification code and the update code; receiving an unlock password through the input apparatus; comparing the unlock password received from the input apparatus with the generated unlock password; and granting a corresponding permission if the acquired unlock password is consistent with the generated unlock password.