Abstract: An overall and accurate annotation of Deep Web data is the key to Deep Web data integration system. However, the existing methods of semantic annotation are unavailable to solve the problem well. An approach to semantic annotation based on CPN network is proposed for Deep Web data. By extracting the basic features of attribute values, semantic annotation is implemented with CPN network. At the same time, an effective method is proposed to obtain the attribute values on Deep Web result pages, thus laying a sound foundation for semantic annotation. Experimental results showed that the approach to semantic annotation based on CPN network improves the accuracy and recall.