A method for storing data establishes a blockchain network, a plurality of data blocks being stored on nodes of the blockchain network. The plurality of data blocks is stored in batches to form a plurality of data segments according to a preset storage period. Each data segment written to the blockchain network is encrypted and newly added data blocks are synchronized with the data blocks which are not stored in the data segment. The newly added data blocks, together with the data blocks not yet stored as the data segment are stored after the commencement of the storage period. A data storage device is also provided.