The invention relates to the technical field of air conditioner upgrading, and provides an encrypted OTA upgrading method for an air conditioner controller, which comprises the following steps: generating model keys corresponding to different model identifiers, constructing a multi-level intermediate key corresponding to different area identifiers and upgrading batch identifiers, pre-encrypting an original
firmware package layer by layer, and updating the
firmware package layer by layer; generating batch-level encrypted packets stored in a classified manner; receiving an
upgrade request carrying equipment identity information, matching a target batch-level encrypted packet, issuing a dynamic
revocation list abstract, generating a unique
session key of a
single session based on joint negotiation of an equipment random number and a cloud random number, performing block
encryption on the batch-level encrypted packet, and issuing the encrypted packet; decrypting the received encrypted blocks layer by layer by using the
session key and a locally stored key of a corresponding level, and restoring to obtain original
firmware blocks; and writing the restored firmware into a
backup partition, and executing partition switching update after determining that the new firmware has a starting condition.