With the development of big data and artificial intelligence applications, data are growing explosively, and the demand for data storage is increasing day by day. The capacity of traditional memory technology is approaching the limit of its physical storage density. Non-volatile memory is expected to replace traditional dynamic random access memory or disk technology due to its excellent characteristics such as byte addressability, low energy consumption, and fast read and write speed. However, the storage medium itself has some shortcomings, such as limited lifetime, asymmetric read and write speed, uneven wear and various sources of errors. The storage principles of common non-volatile memories are explained, and existing improved technologies are investigated and summarized.