A data storage device with a FLASH memory and an operating method for the data storage device are disclosed. According to the disclosure, the space of the FLASH memory is allocated to include groups of data blocks, a plurality of shared cache blocks (SCBs) and a plurality of dedicated cache blocks (DCBs). Each SCB is shared by one group of data blocks, for the write data storage when any data block of the group of data blocks is exhausted. The DCBs are allocated for the hot data storage. Each DCB corresponds to one hot logical block.