With the continuous development of digital technology, the digitalisation and intelligent processing of design history materials have gradually become research topics. In light of the deficiencies in the treatment of large-scale, complex and diverse historical materials for design by traditional methods, this paper puts forward an intelligent semantic annotation and knowledge graph construction method based on natural language processing (NLP). Compare the processing speed of the proposed way and that of the traditional Transformer algorithm through experiments. Based on the emotional information in the historical materials of design, an experiment has been conducted on text emotional analysis to verify the accuracy of the method. Based on the above experiments, this way of operation is much more efficient in terms of runtime and can process the text data for design more promptly. This way is also relatively precise in terms of area for text emotion analysis, and rich emotional information can be obtained from historical materials. The approach of intelligent semantic annotation and knowledge graph construction for design historical materials proposed in this paper enhances processing efficiency, improves the accuracy of emotional analysis, and promotes the digitalisation and intelligence of design historical materials.