A method and apparatus for expanding cloud volume, and a device and a readable medium are provided. The method includes: determining whether there is an request of a host in a cloud volume and confirming a snapshot started during cloud backup (S1); in response to there being no IO request, expanding a snapshot volume of the snapshot started during the cloud backup and the cloud volume (S2); expanding a bitmap of the snapshot started during the cloud backup, and setting a bitmap obtained by expanding as a first preset value (S3); after completion of a cloud backup task, expanding a snapshot volume of an another snapshot that is not started in the cloud backup (S4); and expanding a bitmap of the another snapshot that is not started in the the present cloud backup, and setting a bitmap obtained by expanding as a second preset value (S5).