Hi @Zinc Gao ,
Thank you for reaching out to Microsoft Q&A forum!
Unfortunately, there is no export option available for custom extraction models, but Copy option available, see below:
To move the trained models from one environment to another. The Copy API enables this scenario by allowing you to copy custom models from one Document Intelligence account or into others, which can exist in any supported geographical region. Follow this document for detailed instructions. The copy operation is limited to copying models within the specific cloud environment the model was trained in. For instance, copying models from the public cloud to the Azure Government clod isn't supported.
I hope this additional information helps! Thank you.