The invention discloses a hot backup method and system for data. The system comprises a host and a backup machine. The host is used for generating data to be backed up, adding serial numbers to data to be backed up, and sending them to the backup machine. The backup machine is used for examining serial numbers after receiving data and backing up or buffering data after validation passes, deleting data if not and sending data to the host again. By adoption of the above mode, the hot backup method and system for data have following beneficial effects: the backup machine is capable of timely finding out and reflecting specific data required by the host to be backed up when a backup list is unstable or data volume is super-large or the backup machine is lack of data and abnormal; and therefore stability and effectiveness of hot backup are ensured.