Deep neural networks (DNNs) condense the wisdom of the designer and consume a lot of data and computing resources. It is an important artificial intelligence technology, and is widely applied in our daily life. However, as a digital asset, how to protect DNN models from being illegally copied, distributed or abused (that is, intellectual property protection) is a difficult problem that must
be faced and solved in the process of artificial intelligence industrialization. This article reviews digital watermarking techniques for
intellectual property protection of DNN models. By summarizing the development status of deep model watermarking, the research
trend of deep model watermarking is further prospected.