The invention discloses a data equalizing method and device for a server cluster. The specific implementation mode of the method comprises the steps that expansion on the server cluster is responded, and at least source disk storing to-be-migrated data and a target disk for storing the to-be-migrated data are determined, wherein the source disks are located in at least one original server of the server cluster before expansion, and the target disk is located in a new server in the server cluster obtained after expansion; the new server is forbidden to receive a read-write request on the target disk, and a migration operation of migrating the to-be-migrated data from the source disks to the target disk is executed; when the target disk meets the preset condition that the remaining capacity of the target disk is the same as the average disk remaining capacity of the source disks, the migration operation stops being executed, wherein the average disk remaining capacity is obtained by dividing the sum of the source disk remaining capacities by the number of the source disks. The purpose that the expanded server cluster reaches data equalizing in a short time is achieved, and the cost is reduced.