A device and a method for compressing data by a device are provided, which relate to the storage field and are used to resolve a prior-art problem that a compression ratio at which data in a data block is compressed by a device is relatively low. The method includes: parsing, by a device, an information block in a data block, to obtain a file type of data in the data block and a data sub-block that is included in the data block; determining a characteristic of data in the data sub-block according to the file type; selecting, according to the characteristic, a target compression algorithm that is used to compress the data in the data sub-block; and compressing the data in the data sub-block by using the target compression algorithm. Embodiments of the present disclosure are used to compress data.