A system and a method for accessing and verifying the validity of data content stored in the cache memory on disk are proposed, which is applied in a data accessing system through the use of a master disk controller or a slave disk controller. For data accessing purposes, the master and the slave disk controllers each have a storage space in the cache memory on disk, to temporarily store and access related data. The method for accessing and verifying the validity of data content stored in the cache memory on disk includes: creating a recording area for recording access records on the disk accessed by the disk controller; reading the access record in the recording area, and determining whether the access record shows that the disk was accessed by the master controller upon power-on; wherein, if the record shows that the disk was accessed by the master disk controller, making the master disk controller access the disk with the content stored in the storage space in the cache memory of master disk controller, and, in contrast, if the record shows that the disk was accessed by the slave disk controller, after power-on, making the master disk controller treat the content stored in the storage space in the cache memory of master disk controller as invalid.