A disk array system and a data processing method are provided. The data processing method is applied to the disk array system. The disk array system includes a first disk and a second disk. The data processing method includes: receiving a reading command, wherein the reading, command includes a data starting address; determining to assign the reading command to the first disk or the second disk according to the data starting address of the reading command and a stripe size; and reading corresponding data according to the reading command from the first disk or the second disk which receives the reading command.