The invention discloses a data storage method of a data filtering storage device, which comprises the following steps of: 1) writing data information into a writing unit of a controller, and reading the data information by a reading unit of the controller; 2) enabling the read data information to pass through a data filtering unit, and judging whether the read data information is data informationalready stored in a target block in a flash memory unit or not by the data filtering unit; 3) if not, judging that the read data information is new unread new data information, and storing the new data information into the target block in the flash memory unit; and (4) if so, judging that the read data information is old data information, filtering the data information, storing the data information into an auxiliary target block in the flash memory unit, and feeding back the data information to the write-in unit by the auxiliary target block, thereby forming a data filtering feedback system. Repeated writing of data information is avoided, the read-write efficiency of the data storage device is improved, the storage pressure of the flash memory unit is reduced, and the storage relative capacity of the flash memory unit is effectively increased.