The gap between information production and data storage capacity is continuously growing, so there is an urgent need for new methods of high-density, persistent data storage. With advances in DNA synthesis and sequencing, attempts have been made to use synthetic DNA for data storage and information exchange. DNA storage has many advantages compared with hard disk information storage, including high information density specificity (data bits per gram) and long storage time. Using different algorithmic strategies, text, images, audio, and movies have been encoded into synthetic DNA for storage. In addition to big data storage applications, DNA may be valuable in the exchange of classified information. This review summarizes the basic principles of DNA data storage, introduces research progress into DNA storage in vitro,and analyzes works concerning data size, logic density, and DNA synthesis. We also describe in vivo molecular memory systems, including the adoption of CRISPR to design the DNA storage system. Finally, we discuss various influencing factors and challenges of data storage systems based on DNA.