A method of generating a Firmware Over-The-Air (FOTA) upgrade package is disclosed, comprising: determining whether a file having a same filename or being similar as a file in a software package of a new version exists in a software package of an old version; when there exists a file having a same filename or a similar file, generating a difference file between the file in the software package of the old version and the file in the software package of the new version and adding the difference file into the FOTA upgrade package, and when there doesn't exist a file having a same filename or a similar file, adding the file in the software package of the new version into the FOTA upgrade package. An FOTA upgrading method, a server, and a mobile terminal are also disclosed.