Reversible data hiding is a technique that embeds important data into cover multimedia, such as image, audio, video, and so on. In the sender side, the data is embedded by the reversible transform, and in the receiver side, the data is extracted by the inverse transform. The carrier can be recovered successfully at the same time. So the good performance makes it popular in data hiding on medical image, legal image, and so on. This paper summarizes the existing typical reversible data hiding algorithms, and gives the basic procedure of them.