Multimodal documents, which are among the most prevalent data formats, combine a large amount of textual and visual content. Extracting structured triples knowledge from these documents is a highly valuable task, aimed at helping users efficiently acquire key entities and their relationships. However, existing methods face limitations in simultaneously processing long textual content and multiple associated images for triple extraction. Therefore, we propose a Multimodal Document-level Triple Extraction (MDocTE) framework. Specifically, we introduce a dynamic document graph construction method that extends the model’s scope to the entire document and the external world, while adaptively optimizing the graph structure. Next, we inject the global information and external knowledge learned by the graph neural network into the large language model, generating structured triples after deep interaction. Finally, we design a multimodal relation-aware mechanism and loss function to guide the model in reflecting on the shared information between text and visuals. We release a new triple extraction dataset for multimodal documents and conduct extensive experiments. The results demonstrate that the proposed framework outperforms the state-of-the-art baselines, thus filling the gap in multimodal document extraction. Our data is available at https://github.com/XiangLiphd/Triple-extraction-dataset-for-multimodal-documents.