Abstract: A data reading and writing method based on a variable length cache line. A lookup table stores cache line information of each request. When a read task arrives at the cache, the cache line information is obtained according to the request index, and the request is hit. The data in the cache is read and sent to the requester in multiple cycles, otherwise the request is not in the cache, some read requests are created and sent. The offset, tag and cache line size are recorded in the record of the lookup table, and the request is sent to the DRAM. Once all the data is returned and written to the cache, the corresponding record of the lookup table is set to be valid.